Acceptance and commitment therapy applied to early psychosis: Therapeutic foundations and a narrative systematic review

Abstract

BACKGROUND

Acceptance and commitment therapy (ACT) is a third-generation therapy that appears to be a promising psychological intervention for psychotic disorders. While several systematic reviews and meta-analyses that address the efficacy of ACT for psychosis have been conducted, no systematic review has specifically focused on the application of ACT to the early stages of psychosis.

AIM

To review the state of the art regarding the feasibility and efficacy of treating early psychosis (EP) with ACT-based interventions.

METHODS

First, we describe the foundations of the ACT model to provide the background required to contextualize the main objective of this review. Second, we searched the PubMed and PsycINFO databases for studies published up to January 2025 and identified eight studies that met our selection criteria. The systematic review was conducted in accordance with the PRISMA guidelines and the critical appraisal checklist provided by the Joanna Briggs Institute for randomized controlled trials (RCTs).

RESULTS

All studies were published after 2019. Among the reviewed studies, five were RCTs with a total combined sample of 399 nonoverlapping participants. The methodological quality was moderate for RCTs. The results showed that ACT-based treatments are feasible and improve psychotic symptoms, medication adherence, and global functioning in patients with EP. Furthermore, preliminary evidence exists for the benefits of group-based and online-delivered programs and those that combine face-to-face therapy with novel real-time digital interventions, such as “ecological momentary intervention”, to apply therapeutic concepts to real life.

CONCLUSION

ACT-based treatments in the early stages of psychosis are feasible and improve symptoms, treatment adherence, and self-care skills. Although promising, these results are inconclusive. Further research is required.

Key Words: Acceptance and commitment therapy; Acceptance-based therapy; Early psychosis; First-episode psychosis; Schizophrenia; Ecological momentary intervention; Digital intervention; Systematic review

Core Tip: Acceptance and commitment therapy (ACT) is a promising intervention for the treatment of psychotic disorders, but research on its application to the early stages of the disease is still limited. This study reviews the current understanding of ACT-based interventions for the early phases of psychosis. ACT applied to early psychosis is feasible and improves psychotic symptoms, treatment adherence, and functioning. Furthermore, preliminary evidence indicates the benefits of group-based, online-delivered, and hybrid interventions that combine face-to-face treatment with innovative real-time digital interventions. Although promising, further research should confirm these preliminary findings.

INTRODUCTION

Early psychosis (EP) is the first time a person experiences a psychotic episode. Psychotic disorders are severe and debilitating mental disorders which are often characterized by delusions, hallucinations, disorganized behavior, cognitive impairment, functional deficits, and reduced quality of life[1,2]. People with these disorders experience limited access to medical care, maintain unhealthy lifestyles, and face several biological factors, contributing to an average life expectancy reduction of 14.5 years[2]. Psychotic disorders, including schizophrenia, affect approximately 3.5% of the global population and are associated with significant stigma, functional impairments, and considerable disability[3]. These disorders typically first appear during late adolescence or in the patient’s 20 s or 30 s[4].

The first psychotic episode is defined as the initial period onset of symptoms lasting at least one week, considerably disrupting a person’s daily functioning[5]. The subsequent 2- to 5-year period is critical for prognosis and recovery[5,6]. During this phase, early psychopharmacological, psychological, and psychosocial interventions can lead to substantial improvements, making it the most responsive for therapeutic intervention[7]. However, despite period’s significance, early recognition remains challenging because of low disease awareness and misinterpretation of prodromal symptoms[6]. These barriers delay intervention and contribute to poor prognosis of these individuals[5,6].

While antipsychotic medications remain the first-line interventions for psychotic disorders, pharmacological treatment alone provides limited symptom improvement[2,3]. Therefore, clinical guidelines from the National Institute for Health and Care Excellence and the American Psychiatric Association recommend a combined approaching, integrating pharmacological and psychosocial approaches with psychiatric rehabilitation practices to improve the everyday functioning of these patients[2,8-11]. This comprehensive approach is particularly relevant during the early stages of psychosis[7].

Acceptance and commitment therapy (ACT) represents the principal exponent of third-generation therapies (also called contextual therapies[12-15]). Currently, ACT has accumulated the most empirical research[16]. More than 1100 randomized controlled trials (RCTs) have demonstrated ACT’s effectiveness for treating anxiety and depression[17-19], other psychiatric disorders[20-22], chronic pain, and more ordinary psychosocial problems[16,23,24]. Additionally, ACT has proven its efficacy even in digital self-help formats[25], and scientific support for its efficacy in diverse populations, including children and adolescents, is increasing[16,26,27]. ACT has demonstrated comparable efficacy with traditional cognitive-behavioral therapy (CBT) and may even outperform other active treatments[20].

ACT for psychosis

This section outlines the foundations of the ACT model and its adaptations for better management and analysis of psychotic disorders, with a particular emphasis on their early phases. The following sub-sections provide sufficient background to contextualize this review’s primary objective: Assessing the current state of research on ACT-based interventions for the early stages of psychosis.

The Australian Psychological Society classifies ACT for psychosis (ACTp) as a “Level II” evidence-based psychological intervention[28]. Likewise, Morris et al[21] demonstrated that over the past 20 years, in a variety of therapeutic settings, ACTp significantly improves outcomes on depression, rehospitalization, subjective distress[29-32], and positive symptom management[3,33-36].

ACTp is a promising, pragmatic, and process-oriented intervention model that differs from CBT for psychosis by placing less emphasis on reassessing unusual experiences, situations, or interpretations. Instead, ACTp encourages people to respond to their experiences in an “open, mindful, and active way”, promoting skillful action based on personal values[21,37]. Because of this value-based approach, ACTp aligns closely with personal recovery principles[21,38,39].

Furthermore, ACTp is an innovative psychotherapeutic approach designed to enhance engagement and improve comprehension in individuals with psychosis. This makes it particularly beneficial for patients with cognitive impairments, low uncertainty thresholds, histories of trauma, or paranoid thinking. By modifying conventional therapeutic techniques, ACTp enhances understanding and treatment outcomes in its target population[40]. Rather than a collection of techniques, ACTp is a conceptual model that defines psychotic problems in terms of psychological inflexibility[41-43]. This inflexibility limits an individual’s ability to adapt to life circumstances, driven by excessive experiential avoidance, rigid interpretations of private experiences, lack of clarity about life goals, and difficulty committing to long-term and effective actions[44].

In this sense, ACT-based interventions show promise in promoting recovery and preventing following first-episode psychosis (FEP) by enhancing psychological flexibility (PF). This is achieved through strategies centered on acceptance, mindfulness, and behavioral activation, all of which with a focus on personal values and meaningful life goals[44-46]. ACTp makes two important contributions to the literature. First, it helps people differentiate between internal events (thoughts and feelings) and the part of the “self” living with these experiences. Essentially, people suffering from psychosis will find it easier to gain greater acceptance of their problems and distance themselves from critical self-evaluations and self-stigma. Second, ACTp weakens the control of distressing experience over an individual’s decisions and actions, promoting more adaptive coping mechanisms[44].

Additionally, ACTp reduces the extent to which beliefs and symptoms influence daily experiences and behaviors[47]. Unlike approaches that rely heavily on logical analysis procedures, ACTp integrates experiential exercises, metaphors, and behavioral tasks to achieve changes in patients[21,48]. ACTp highlights PF through the six core processes defined in ACT[14]: Acceptance, cognitive defusion, present-moment awareness, self-as-context, personal values, and committed action[48]. Figure 1 represents the “Hexaflex model”, which explains the interaction among the six core processes[14]. Table 1 summarizes the essential therapeutic components.

Figure 1 The “Hexaflex model”. This figure illustrates the interaction between the six core processes in acceptance and commitment therapy. Adapted from Hayes and Lillis[14].

Table 1 Essential components of the therapeutic process of acceptance and commitment therapy for psychosis.

Therapeutic elements	Main goals
Create a state of creative hopelessness	The goal is for patients to pay attention to their strategies for solving their problems and how these strategies ultimately failed
Raise the possibility that “the problem is control”	The patients should now understand that certain aspects of their experience (emotions, thoughts, memories) cannot be controlled. The use of central metaphors is recommended
Create a distance from the language (defusion)	Starting to doubt aspects other than hallucinations or delusions is one way to get patients to distance themselves from their experiences
Help create a transcendent sense of self (“self as context”)	Focus intervention on enhancing “self as context.” ACT techniques focus primarily on strengthening the sense of “self as context” instead of “self as content”
To clarify and strengthen the patient’s values	Look for conditions in which a person with psychosis can pursue these values despite their circumstances (e.g., symptoms). Materialize these values in actions aimed at achieving them
Develop willpower	The will presupposes a hierarchical organization of ends and places the person in front of the troubled and, therefore, the inevitably tragic character of existence. Therapy is placed in the context of the person's life, and relapses are included as an additional aspect

ACT: Acceptance and commitment therapy.

Proposed mechanisms of change in ACTp

Several studies have explored the underlying mechanisms that drive ACTp’s effectiveness[41], while others have examined the possible mediators and moderators of its outcomes[43].

PF has consistently been identified as ACTp’s primary mechanism of change[41,48]. Thomas et al[47] proposed several mechanisms of action for ACTp (Figure 2); nevertheless, subsequent studies have only partially validated these hypotheses[35]. However, recent studies support some of these mechanisms[41,44].

Figure 2 Hypothesized mechanisms of action of acceptance and commitment therapy for psychosis. Adapted from Thomas et al[47]. Acceptance and defusion reduce preoccupation, conviction, distress, and life interference related to positive symptoms and improve them. Engaging in values-based actions promotes adaptive behavioral changes and improves negative symptoms. The network of changes leads to an overall improvement in mental state and social functioning. ACT: Acceptance and commitment therapy.

Pittman et al[41] conducted a systematic review and meta-analysis of the relationship between psychosis, PF, and other key ACTp therapeutic processes. The analysis included 35 studies, primarily cross-sectional and of moderate methodological quality. Meta-analyses revealed that PF had a large effect size on paranoia, a moderate effect on delusions, and a small effect on auditory hallucinations. When between-group differences (psychosis vs controls) were compared, PF showed a moderate effect size in favor of controls. Cognitive fusion was significantly associated with paranoia. Overall, this review showed that psychological inflexibility was linked to a range of psychotic symptoms across the psychosis continuum. Moreover, this study also demonstrated how these processes may interact with other psychological trends or risk factors associated with psychosis[41]. Notably, a recent study used an “ecological momentary assessment” approach to evaluate state levels of acceptance and mindfulness, monitoring their association with state fluctuations in symptoms[49]. Their results show that mindfulness skills are associated with symptoms in real time. Moreover, research has highlighted the importance of acceptance-based interventions for psychotic disorders, particularly when mood symptoms are present[50].

Relative to the theorized mediators and moderators of ACT, studies on outpatients suffering from depression and psychosis have revealed that improvements in depression were correlated with increased PF, mindfulness, and a “valued life” throughout treatment[51]. Additionally, other issues, such as believability in hallucinations (worsening), “openness to the present moment”, and better therapeutic alliance (improving), could moderate therapeutic outcomes[21,52].

Finally, a recent study investigated whether sociodemographic factors, personality traits, or trauma history influenced clinical outcomes in EP patients receiving an ACT-based intervention[53]. Results indicated that personality traits (e.g., extraversion) and sociodemographic factors (e.g., educational attainment) may predict clinical outcomes including PF, negative symptoms, and global functioning. Additionally, greater emotional regulation flexibility correlates with more stable negative emotions and faster emotional recovery in EP patients[54].

ACTp in routine clinical practice

Routine clinical settings-based research on the implementation of ACTp remains limited[21,55]. The ACT model aligns with recovery from severe mental conditions[56], defined as “living a satisfying, hopeful, and contributive life, even with the limitations caused by the illness, and having a sense of purpose and direction” and is therefore appropriate for people with psychosis[56,57].

Based on this model, Johns et al[56] developed an intervention (the “ACT for life”) to promote PF in response to psychotic symptoms and related emotions, encouraging alignment with personal values. Using a standardized protocol, this study evaluated the effectiveness of a brief ACT group intervention for individuals with psychosis in a community mental health setting. The intervention was conducted over 4-8 weeks, with a telephone booster session at 10 weeks. This pilot study’s results showed that the implementation of ACT groups for patients with psychosis in routine practice within community mental health services was feasible. These groups were acceptable for patients with EP and those with established illness. Moreover, patients were very positive regarding the intervention. Psychosocial functioning and mood were improved, with a medium effect size[56]. Consistent with the ACT model, patients reported greater PF after treatment. Moreover, this approach has also been adapted for people with psychosis and their caregivers, demonstrating applicability in routine clinical practice within community mental health settings[57]. Farhall et al[42] measured improvements in personal recovery, well-being, and PF, concluding that ACT is feasible, acceptable, effective, and safe for use in public mental health services.

Morris and Oliver[45], in their seminal work, argued for integrating acceptance- and mindfulness-based interventions linked to behavioral principles into early intervention services. These should focus on recovery guided by values and meaningful goals. The authors advocated normalizing skill training to foster value-consistent lifestyles. Additionally, they emphasized the building of six key skills: (1) Learning to live in the moment; (2) Identifying choices in every moment; (3) Continuing to engage in meaningful pursuits; (4) Recognizing when one’s mind is helping oneself and when it is not; (5) Accepting the unchangeable; and (6) Being compassionate with oneself[45].

Implementing ACT into the early diagnosis and treatment of patients with FEP leads to fewer rehospitalizations and improved psychosocial functioning across inpatient and outpatient settings[58]. Moreover, psychoeducation and group ACT have proven effective as psychological support strategies for the informal caregivers of FEP patients[59].

ACT for emotion regulation in EP

Emotional dysfunction is a frequent but often overlooked consequence of psychosis that significantly influences symptom exacerbation, relapse, and recovery[60]. This dysfunction includes depression, commonly accompanied by hopelessness and suicidal ideation; social anxiety, characterized by intense fear of social interactions and relationship-building difficulties; and trauma-related symptoms, particularly intrusive images and memories around the lived psychotic episode and its treatment[51].

To address emotion regulation in people with EP, Khoury et al[60] developed an ACT-based treatment protocol. This intervention comprised eight weekly group sessions, each spanning 60-75 minutes, integrating the core principles of third-generation therapies, including compassion, acceptance, and mindfulness. The study reported significant improvements in overall emotion regulation, with notable effects on self-blame, rumination, and “catastrophizing” among participants at the 3-month follow-up. While positive symptoms showed slight improvement at follow-up, anxiety and depression demonstrated moderate to large reductions.

Regarding adaptations for FEP patients, Khoury et al[60] emphasized two key considerations: (1) The practice of mindfulness and meditation should be limited to 15 minutes to minimize the risk of triggering intense psychotic symptoms; and (2) It is preferable not to use abstract materials, such as metaphors, as it may be challenging because of the cognitive difficulties that some patients may experience. However, Simsion et al[61] recommend using a “core metaphor” adapted to the conditions of the patients targeted by the intervention.

Aims and rationale

The previous sections outlined the fundamental principles of ACTp, provided to better understand the following sections, wherein we will develop the results of the primary aim of this review: Assessing the current state of research on ACT-based interventions for the early stages of psychosis.

Research on ACT for EP remains limited. While several systematic reviews and meta-analyses that address the efficacy of ACTp have been conducted[21], no systematic review has specifically focused on the application of ACT to EP.

Given the critical need for evidence-based interventions in early intervention psychosis care and the lack of comprehensive reviews on ACT applied to EP, this study aimed to outline the contributions of ACT to the treatment of the early stages of psychosis. Furthermore, as this is a new research field, the findings are discussed in the context of the literature on ACTp.

A preliminary search of PROSPERO did not identify any current or ongoing systematic reviews on this topic.

MATERIALS AND METHODS

This systematic review was conducted in accordance with the PRISMA guidelines[62].

Search strategy

The PubMed and PsycINFO databases were searched. The search period was up to January 2025, and we included references in all languages. The reference lists of all sources of evidence were screened for additional studies.

The search terms used for searches in the PubMed database were as follows: [“acceptance and commitment therapy” (All Fields)] OR [“acceptance-based interventions” (All Fields)] AND [“early psychosis” (All Fields)] OR [“first episode psychosis” (All Fields)] OR [“recent onset psychosis” (All Fields)] OR [“early-stage psychosis” (All Fields)]. This search strategy was adapted for use in each database searched.

A final search was conducted for studies published through April 2025 to avoid missing relevant records during the study period (most recent access: 2025-04-18). No new sources were identified.

To ensure comprehensive coverage, we also explore the literature on ACTp (both empirical and review studies), allowing for detailed discussion of findings in this broader context.

Study selection

The primary question was “Is there evidence about the acceptability, feasibility, and efficacy of ACT-based interventions applied to EP, FEP, recent-onset psychosis, or early stages of psychosis?”. Table 2 provides an overview of the review’s objectives and selection criteria (Participants, interventions, comparators, outcomes, and study design).

Table 2 Participants, interventions, comparators, outcomes, study design.

Category	Description
P: Participants	People with psychotic disorders in their early stages. People with subthreshold psychotic symptoms
I: Intervention	Acceptance and commitment therapy or acceptance-based therapy for psychosis
C: Comparison	Comparison with other types of therapeutic intervention, TAU, or control groups
O: Outcomes	Changes in positive, negative, general, and mood symptoms; changes in psychosocial functionality; treatment adherence; feasibility; acceptability; rehospitalizations; improvement in coping with symptoms; changes in psychological flexibility
S: Study design	Randomized controlled trials, open trials, preliminary studies, or quasi-experimental studies. Secondary analysis from RCTs

TAU: Treatment as usual; RCT: Randomized controlled trial.

The full text of the selected citations was independently assessed by Pena-Garijo J and Baeza-Mor T (the first and second authors) according to the inclusion criteria. Any disagreements were resolved through discussion and by Martinez-Raga J (the third author).

Out of 31 studies, 21 were eligible for assessment after removing duplicates. Ultimately, eight studies met the selection criteria and were included in this narrative and systematic review. Figure 3 shows the PRISMA flow diagram of search and study selection process.

Figure 3 PRISMA flow diagram of search and study selection process.

Assessment of methodological quality

Pena-Garijo J and Baeza-Mor T assessed the methodological quality of studies following the critical appraisal checklist provided by the Joanna Briggs Institute (JBI) for RCTs[63]. This method has been used in previous systematic reviews of the use of ACT in psychosis[3]. Each item was resolved with a “yes” (1 point) or “no”, “unclear” or “not applicable” (0 points). The sum of items provides an overall score from 0 to 10 points (the higher the score, the better the study quality). Martinez-Raga J oversaw the methodological quality assessment and resolved any discrepancies. The checklist contains 13 questions covering two domains: Internal validity, related to four methodological biases (items 1 to 10) and statistical validity (items 11 to 13). Items 11 to 13 are not included in the overall score, as they do not assess internal validity[63].

Data synthesis

Due to variations among the studies in their outcome measures, methods, and assessment tools, as well as their relatively small sample sizes, statistical pooling was not possible, and a meta-analysis could not be performed. The findings are presented in a narrative form and in tables to aid in data presentation.

The study protocol for this systematic review was registered in PROSPERO (PROSPERO 2025 CRD420251035365. Available from: https://www.crd.york.ac.uk/PROSPERO/view/CRD420251035365).

RESULTS

Five of the eight studies included in the systematic review were RCTs. All were published after 2019. The sample sizes varied from 55 to 148, with a total combined sample of 399 nonoverlapping participants.

Most studies (n = 5) investigated the “ACT in Daily Life” (ACT-DL), a digital health intervention applied to individuals with EP[64]. These results were based on trials and secondary analyses of the INTERACT study dataset[54,65-68]. Another study evaluated acceptance-based, insight-inducing medication adherence therapy (AIM-AT) to improve medication adherence in patients with EP[69]. One RCT assessed the effectiveness of an eight-session online ACT-based group therapy program[7]. Finally, another RCT focused on a 5-week group ACT-based lifestyle counseling program (ACT-LCP) designed to improve motivation for healthy living[70]. Table 3 summarizes the key articles.

Table 3 Summary of reviewed studies on acceptance and commitment therapy in early psychosis.

Ref.	Des.	Participants/samples	Population	Intervention	Conclusions	Results
Vaessen et al[65]	No RCT	n = 16. No control group	People with ultra-high risk (clinically established) or first-episode psychosis	ACT in Daily Life (ACT-DL): A new mobile health treatment protocol for people with early psychosis. The protocol was designed to facilitate the translation of therapeutic techniques learned during in-person ACT sessions into the patient’s daily life	ACT-DL may aid individuals in integrating skills they learn during therapy sessions into their everyday lives. ACT-DL may help early psychosis patients by applying ACT skills to different contexts of everyday life. Adherence to the protocol was relatively demanding	Participants evaluated the overall training (M = 5.63 ± 1.17), the ACT therapy sessions (M = 5.63 ± 1.36), and home exercises (M = 4.81 ± 1.63) as useful. Moreover, participants evaluated the app as useful (M = 4.56 ± 1.69) and reported that it helped them apply the exercises in daily life (M = 4.75 ± 1.71) and made them more aware of their feelings (M = 5.25 ± 1.56)
Van Aubel et al[66]	RCT	Total n = 55. ACT-DL (n = 27). Active control (n = 28)	Young people (16 to 25) with subthreshold depressive and/or psychotic symptoms	ACT-DL through an app	Depressive symptoms decreased more in ACT-DL than in active control. Self-reported symptoms decreased equally in ACT-DL and active control. ACT-DL did not modify PF	Depression scores (rated by the interviewer) decreased among participants in the ACT-DL group compared with controls (P = 0.027)
Myin-Germeys et al[67]	RCT	Total n = 148 ACT-DL + TAU (n = 71) TAU (n = 77)	People with ultra-high risk (clinically established) or first-episode psychosis	Multicenter INTERACT RCT. ACT-DL combines face-to-face therapy with an ecological momentary intervention (EMI)	The study did not support a significant effect of ACT-DL compared to TAU on primary outcomes However, global functioning and psychotic distress were improved in the ACT-DL group	Results showed that Global functioning (χ2 = 9.05; P = 0.033) and negative symptoms (χ2 = 19.91; P < 0.001) improved in ACT-DL compared to TAU, as did psychotic distress (χ2 = 21.56; P < 0.001) measured as EMI
van Aubel et al[68]	No RCT	n = 71. No control group	People with ultra-high risk (clinically established) or FEP	No intervention. Data on treatment engagement with and acceptability of ACT-DL during and after the intervention of ACT-DL. This study is a secondary analysis of the INTERACT trial	The study showed good treatment engagement with and acceptability of ACT-DL in early psychosis. Participants attended an encouraging number of face-to-face sessions and weekly interactions. Results suggested an effective real-world application of ACT techniques. Moreover, ACT-DL improved emotional awareness	The results demonstrated high levels of commitment and participation among the participants, with the majority (n = 42) completing all sessions. In addition, 86% to 96% of subjects rated the sessions and exercises as useful
Chien et al[69]	RCT	Total n = 126. AIM-AT (n = 42) Psychoeducation (n = 42) TAU (n = 42)	Outpatients with psychosis ≤ 3 years’ duration	Acceptance-based intervention plus motivational interviewing to improve medication adherence for people with early psychosis (AIM-AT)	Compared to the other two groups, participants in the AIM-AT experienced significant improvements in primary outcomes (medication adherence and knowledge of the disease). The AIM-AT group was also better in psychotic symptoms, psychosocial functioning, satisfaction with service, duration of hospitalization, and number of patients hospitalized during the follow-up	Compared with psychoeducation and/or TAU, the AIM-AT group had more significant improvements, with moderate to large effect sizes (η2 = 0.07–0.18). Adherence: η2 = 0.18. Insight: η2 = 0.10. Psychotic symptoms (PANSS): η2 = 0.12. Functioning (SLOF): η2 = 0.09. Length of hospitalization: η2 = 0.09
Özer and Dişsiz[7]	RCT	Total n = 53. ACT (n = 26) TAU (n = 27)	People with schizophrenia and other psychotic disorders with less than 3 years of duration	8-session ACT program as an online group therapy	Online group ACT applied to individuals with early psychosis was found to reduce psychotic symptoms and increase their levels of functioning. Hospitalizations were also found to be lower in the intervention group	Differences in post-test and follow-up on symptoms (total PANSS): χ2 = 42.66; P = 0.000. Effect size in between-group differences: Positive symptoms (W = 0.80); Negative symptoms (W = 0.65); General symptoms (W = 0.86). Differences in social functioning: χ2 = 42.67; P = 0.000. Effect size: W = 0.821
Li et al[54]	No RCT	n = 148. No control group	Individuals were at high clinical risk for psychosis or with first-episode psychosis	Data obtained from the INTERACT study baseline assessment, during which all participants completed 6 days of experience sampling assessment of momentary negative affect and assessments of emotion regulation strategy use	The study demonstrated that greater emotion regulation (ER) flexibility predicts more stable negative emotions and faster affective recovery. Findings further provide evidence for ER flexibility in early psychosis, emphasizing the adaptive nature of regulatory flexibility to reduced instability in negative affect (NA) and faster recovery from NA in everyday life	At the intrapersonal level, results show significant associations between lower NA instability and higher ER flexibility (P = 0.049). However, the opposite pattern is observed at the interpersonal level: Higher NA instability is associated with greater ER flexibility (P < 0.001)
Chong et al[70]	RCT	Total n = 72. ACT-LCP (n = 36). Active control (n = 37)	Early psychosis patients	Five-week group program focusing on ACT-based motivation for healthy lifestyles: ACT-based Lifestyle Counselling Program (ACT-LCP)	The ACT-LCP was feasible and acceptable, demonstrating initial efficacy in individuals with early psychosis. Improvements were observed in PF, autonomous motivation, psychotic symptoms, and quality of life at 12 weeks post-intervention	Significant improvements in ACT-LCP participants compared to controls at the 12-month follow-up in terms of physical activity (P < 0.001), autonomous motivation (aMD = 4.74; P < 0.001), psychological inflexibility (aMD = -7.69; P < 0.001), mental state (aMD = -6.83; P < 0.001), and quality of life (aMD = 0.46; P = 0.006)

The table includes only the measures that show a significant effect. SMD: Equivalent to Cohen's d; W: Kendall’s W; η²: Eta squared (effect size); M: mean ± SD; aMD: Adjusted mean difference; ACT: Acceptance and commitment therapy; TAU: Treatment as usual; RCT: Randomized controlled trial; FEP: First-episode psychosis; PANSS: Positive and negative syndrome scale; SLOF: Specific level of functioning scale.

.

The RCT’s methodological quality scores ranged from 6 to 8 out of 10 (following the JBI checklist), which suggests moderate methodological quality. Table 4 summarizes the results of the methodological evaluation of the selected RCT studies.

Table 4 Methodological quality appraisal of the randomized controlled trials.

Domain/question	van Aubel et al[66]	Myin-Germeys et al[67]	Chien et al[69]	Özer and Dişsiz[7]	Chong et al[70]
Internal validity. Bias related to:
Selection and allocation
1. Was true randomization used for assignment of participants to treatment groups?	Y	Y	Y	Y	Y
2. Was allocation to treatment groups concealed?	U	Y	Y	Y	Y
3. Were treatment groups similar at the baseline?	Y	U	Y	Y	Y
Administration of intervention/exposure
4. Were participants blind to treatment assignment?	N	N	N	N	N
5. Were those delivering treatment blind to treatment assignment?	Y	Y	U	U	N
6. Were outcomes assessors blind to treatment assignment?	Y	Y	Y	N	U
Assessment, detection, and measurement of the outcome
7. Were treatment groups treated identically other than the intervention of interest?	Y	Y	Y	U	Y
8. Was follow up complete and if not, were differences between groups in terms of their follow up adequately described and analyzed?	Y	Y	Y	Y	Y
9. Were participants analyzed in the groups to which they were randomized?	Y	Y	Y	Y	Y
Participant retention
10. Were outcomes measured in the same way for treatment groups?	Y	Y	Y	Y	Y
Statistical conclusion validity
11. Were outcomes measured in a reliable way?	Y	Y	Y	Y	Y
12. Was appropriate statistical analysis used?	Y	Y	Y	Y	Y
13. Was the trial design appropriate, and any deviations from the standard RCT design accounted for in the conduct and analysis of the trial?	Y	Y	Y	Y	Y
Score	8	8	8	6	7

The classification follows the Joanna Briggs Institute checklist for methodological quality appraisal of randomized controlled trials[63]. Items 11 to 13 are not included in the overall score because they do not evaluate the internal validity. Y: Yes; U: Unclear; N: No.

Synthesis of clinical outcomes

Symptoms: Among RCTs, four studies have found that ACT-based interventions significantly improve psychotic symptoms involving overall mental state[7,69,70], positive[7] and negative symptoms[7,67], general psychopathology[7], and psychotic distress[67]. Moreover, van Aubel et al[66] reported a significant decrease in depression.

Functioning: Compared to treatment as usual (TAU), four RCTs found increased psychosocial functioning[7,67,69] or quality of life[70].

Feasibility: Both RCT and no-RCT studies demonstrated that the ACT-DL intervention was feasible[65-68]. Moreover, the AIM-AT intervention was safe and well-received by the patients with EP[69], and the ACT-LCP was feasible and acceptable[70].

Other outcomes: The AIM-AT intervention showed statistically significant improvements in medication adherence and understanding of the illness and treatment[69], while ACT-LCP demonstrated increased physical activity[70]. Regarding hospitalizations, two studies found that ACT-based interventions reduced the number or length of hospitalizations[7,69]. Only one study reported improvement in PF[70].

ACT-DL

Building on ACT principles, Reininghaus et al[64] developed a treatment protocol that integrated ecological and digital perspectives with previous ACT-based interventions. This protocol combined in-person and online interventions to practice ACT skills in daily life.

INTERACT study protocol

The INTERACT study evaluated the effectiveness of the ACT-DL, a novel ecological momentary intervention (EMI), in a multicenter RCT involving individuals at ultra-high risk for psychosis (UHR) or experiencing FEP[64].

The study aimed to recruit 150 individuals with UHR or FEP from five mental health services in the Netherlands and Belgium. Participants were randomly assigned to either the experimental group (those who received ACT-DL intervention in addition to TAU) or to a control group (received TAU only, which included routine mental health care and CBT for psychosis, where appropriate).

The intervention followed a manualized protocol, consisting of eight ACT training sessions, including one psychoeducation session. These were delivered in-person by a trained clinician and an ACT-based EMI through a smartphone app, reinforcing ACT principles in participants’ daily lives[64].

Results of the INTERACT study

Chronologically, the first study to provide preliminary data on the feasibility of ACT-DL is that of Vaessen et al[65]. Their study outlined a treatment framework designed to help patients develop “more adaptive automatic responses to stressful situations and engaging more in their values by using a smartphone app to apply therapeutic content to their everyday lives”[65]. In the ACT-DL, participants engage in a mobile intervention demanding active practice of ACT skills throughout the day apart from standard sessions. Participants undergo weekly individual ACT sessions. Each weekly session is followed by at least three days of “the mobile phase,” focusing on the components discussed during the in-person sessions. This intervention is ideally suited for a mobile health (mHealth) format based on the experience sampling method (ESM) described by Reininghaus et al[71]. ESM, a structured diary technique, captures daily life experiences. By using this technology, ACT-DL allows patients to apply ACT skills “in the real world and in real time” within their natural circumstances[72]. After completing the program, they were encouraged to use the techniques precisely when needed (e.g., when experiencing distress). Therefore, the intervention is interactive and tailored, adapting to the individual’s mental state and situational context[65]. Table 5 outlines the key components of ACT-DL.

Table 5 Description of the acceptance and commitment therapy in “Daily Life” key components.

Module	Description
Creative hopelessness	Help patients understand that their previous attempts to solve their problems are failing and that they should consider other alternatives. The module contains two different ACT metaphors and four ACT exercises on “creative hopelessness.” The proposed exercises help patients to become more aware of their avoidant coping strategies
Acceptance	Acceptance is presented as an alternative to control and avoidance. Patients are provided with two ACT metaphors and seven ACT exercises focused on the “acceptance” component. These exercises are designed to help them put the theory into practice and experience their feelings and emotions without trying to change them
Cognitive defusion	Cognitive defusion is a chance to distance oneself from one's thoughts. Patients are guided through exercises focusing on observing and distancing from their thoughts. This week's mobile module includes two metaphors about the “cognitive defusion” component and 7 exercises for practicing cognitive defusion. Once patients can detach from their thoughts, they can transfer these strategies to thoughts about the self and let go of their self-image, which is the topic of the next module
Self as context	Distancing from unpleasant beliefs (learned during the cognitive defusion module) is generalized to include beliefs about the self. Once we understand that we are not what we think or feel, we can understand ourselves as observers of pleasant or unpleasant experiences. The self is resistant to change; on the contrary, its content can change. The daily life module for this week focuses on the “self as context” component and includes two metaphors and four “self as context” exercises (instead of “self as content”)
Contact with the present moment	This component helps patients focus less on the past and future and more on the “here and now.” Patients have practiced these skills throughout the other modules. The practice continues during the daily life module the week after this session, where two “contact with the present moment” metaphors remind patients to be aware of the present moment, and the same four exercises they have practiced during the session so far guide them in this process
Values	This module is designed to help people live a life guided by values rather than unpleasant experiences. During this session, patients are invited to think about their personal values, which serve as a guide in life and a pilot for their behavior. This module includes two metaphors from the “values” component. During the three days following the session, patients are supplied with 4 exercises to explore further which values are important to them. Exploring values is necessary to connect with the goal of the next module
Committed action	“Putting theory into practice” is a session dedicated to building meaningful, realistic, specific goals according to the personal values identified in the “values” session. The “committed action” daily life module includes two new metaphors and four new exercises to help patients set and achieve their objectives step by step
Psychological flexibility	The central theme of the last session is to understand how to apply ACT skills “in a flexible manner” to concrete situations, depending on the challenges of the present moment. Patients were given a module summarizing all previous components during this last week. The module contains one metaphor and one exercise related to each component (acceptance, cognitive defusion, values, and committed action)

ACT: Acceptance and commitment therapy.

Treatment evaluation data were available for 16 patients who completed the ACT-DL protocol. Preliminary findings indicated that ACT-DL was both feasible and beneficial in this sample, helping patients integrate ACT techniques into daily life[65]. Participants rated the general training, ACT therapy sessions, and home exercises as valuable. Additionally, the participants found the app useful, reporting that it helped them apply the exercises in daily life and increased their emotional awareness. However, this protocol was considered demanding, which may have influenced adherence.

Building on these findings, van Aubel et al[66] conducted a study of 55 young people with subthreshold depressive and/or psychotic symptoms to evaluate the efficacy of the ACT-DL compared with an active control group. The primary objective was to assess the feasibility of an EMI-enhanced ACT intervention in preventing symptom progression. The secondary objective was to evaluate ACT-DL’s impact on symptoms, PF, and positive and negative affectivity in daily life. Prior controlled studies suggest that ACT yields on mood reported promising results for depression, which is often associated with psychotic symptoms[73-75]. Similarly, Shi et al[76] found that ACT interventions improved self-esteem and PF in individuals with remitted schizophrenia.

This study confirmed that ACT-DL is a feasible intervention with good adherence. Objective depressive symptoms (assessed by the clinician) decreased more in the ACT-DL group compared to the active control group. However, both groups reported similar reductions in psychopathology, and the intervention did not significantly alter PF or positive affect in daily life[66].

Moreover, two additional studies provided the results of secondary analyses from the INTERACT study[54,68].

The first study showed how engaged and acceptable ACT-DL was during and after the intervention in 71 patients who completed the treatment[68]. Participants followed an 8-week in-person training program accompanied by a real-time ecological intervention based on the ACT, which was delivered through a mobile app called PsyMate (cited by van Aubel et al[68]). This application encouraged patients to engage with ACT metaphors, exercises, and on-demand coping strategies when experiencing distress. Additionally, participants could have access to the paper-based ACT exercises. The findings indicated high engagement and strong treatment acceptance for both in-person sessions and ACT-based EMI. Most participants attended all scheduled sessions, but overall engagement with the app varied. This is likely because of individual differences in how patients responded to the notifications. Despite this, participants gave high ratings to both the in-person sessions and the EMI, stating that these helped them become more emotionally aware[68].

The second study analyzed baseline data from the INTERACT study baseline evaluation, wherein participants completed six days of ESM[71] of momentary negative affect and end-of-day measurements of emotion regulation strategy use[54]. Negative affect and stress levels were measured at 10 different time points in the morning. Researchers examined fluctuations, instability, inertia, recovery of negative affect, and flexibility in emotion regulation. The findings revealed that lower instability in daily negative affect correlated with greater flexibility in emotion regulation among individuals with EP. There were no significant differences in the variability. However, a contradictory pattern emerged when individuals were directly compared. Those who reported greater instability and variability in negative affects showed greater flexibility in using emotion regulation strategies. Participants with greater flexibility in using emotion regulation skills demonstrated faster recovery of negative affect. These findings provide further insight into the complex relationship between emotional experiences and regulation strategies in people with psychosis[54].

Finally, Myin-Germeys et al[67] conducted the most comprehensive study using data from the INTERACT study. They assessed the efficacy of the ACT-DL according to the protocol proposed by Reininghaus et al[64]. This multicenter RCT randomly assigned 148 participants into two groups. Participants in the experimental condition attended the ACT-DL intervention, which comprised eight in-person ACT sessions. They also used an EMI app to apply the learned skills in their daily lives. Participants in the TAU condition received standard treatment based on national guidelines, including CBT at some sites. Patients in the ACT-DL group also received TAU (exception for CBT).

The Comprehensive Assessment of At-Risk Mental States[77] did not reveal a more substantial reduction in psychotic distress for the ACT-DL group compared to the TAU group. However, significant improvements in global functioning were identified via the Social and Occupational Functioning Assessment Scale[78], as well as reductions in negative symptoms assessed using the Brief Negative Symptom Scale[79]. Momentary psychotic distress, evaluated through the ESM[71], also showed notable improvement in the ACT-DL group compared with the TAU group at the 6- and 12-month follow-ups.

ACT-based intervention to improve medication adherence

Expert guidelines identify several critical factors influencing medication adherence in psychosis patients: (1) Lack of awareness and/or understanding of the illness; (2) Concerns or anxiety about adverse effects; (3) Perceived low efficacy of the medication in addressing persistent symptoms; and (4) The belief that medication is no longer necessary[69].

A recent RCT investigated the effectiveness of an acceptance-based intervention aimed at improving medication adherence in adults with early-stage psychosis[69]. This intervention integrated components of ACT, psychoeducation[80], and motivational interviewing[81,82].

Programs like motivational interviewing-based medication adherence therapy[83] and acceptance-based disease self-management interventions[84,85] illustrate approaches designed to enhance treatment adherence in psychosis patients. Acceptance-based therapy shifts the focus from altering symptoms and associated disruptive behaviors to transforming patients’ perceptions of their symptoms and the “unwanted” thoughts, feelings, and physical sensations tied to them[69]. Thus, acceptance-based and motivational interviewing could be a rapid, helpful, and effective approach to motivate EP patients to take their prescribed medications[69].

The study enrolled 126 adults diagnosed within the past three years across four community mental health centers in the Hong Kong District. Participants were randomly assigned to one of three groups: The AIM-AT group, which underwent 10 sessions of ACT-based medication adherence therapy; conventional psychoeducation; or the TAU group. Both the AIM-AT and psychoeducation groups also received TAU. The primary outcomes assessed were medication adherence and knowledge about the disease and treatment. Evaluations were conducted at baseline, post-intervention, and at 6- and 12-month follow-ups[69].

The participants in the AIM-AT group underwent a group-format intervention that combined weekly or biweekly motivational interviewing-based sessions with acceptance-based psychoeducation over a duration of four months. Table 6 summarizes the specific content covered in each session.

Table 6 Description of the intervention protocol: Acceptance and commitment therapy-based intervention to improve medication adherence.

Session/content	Session/content
Session 1: Commitment to the group program and understanding of psychosis, treatment, and care	Sessions 4-6: Goal review, mindfulness skill development, addressing medication ambivalence, and enhancing interpersonal and communication skills
Session 2: Introduction to ACT and beliefs about illness and medication	Sessions 7-9: Identifying obstacles to goal attainment, working on acceptance of unpleasant emotional experiences, and learning to break negative thought patterns
Session 3: Improved self-management of psychotic symptoms and negative thoughts, and medical history review	Session 10: Evaluation of changes and self-reflection, development of future plans and practices: “Maintaining effective coping strategies in high-risk life situations” and “behavioral rehearsal of relapse prevention”

AIM-AT: ACT-based intervention to improve medication adherence[69]. ACT: Acceptance and commitment therapy.

The findings indicated that the AIM-AT group achieved significant improvements compared to the TAU group in medication adherence, assessed using the adherence rating scale[86], and knowledge of illness and treatment, measured by the treatment attitude and insight questionnaire[87], across all three time points. When compared to the psychoeducation group, the AIM-AT group also showed improvement in the same variables, although only at the 12-month follow-up. Additionally, the AIM-AT group exhibited enhanced functionality, lower hospitalization rates, and significant improvements in psychotic symptoms relative to the TAU group, both immediately post-treatment and at the 6- and 12-month follow-ups.

Online group-based ACT for psychotic symptoms and functioning levels

Previous studies have highlighted that ACT reduces depression and anxiety in patients during the early stages of psychosis. It also enhances their psychological resilience, fosters independence in daily activities, and thus improves their functionality[66,88].

One particularly compelling study explored the effects of online group-based ACT in enhancing psychotic symptoms and functional outcomes in EP patients[7]. The intervention involved 53 participants diagnosed with schizophrenia or other psychotic disorders within the past 3 years. They were recruited from a cohort of patients who had been previously hospitalized in a Turkish clinic. Participants were randomly assigned to one of two groups: An experimental group that underwent eight sessions of an online ACT intervention or a control group that did not receive any specific intervention from the evaluators. Assessments were performed at three points: Pre-intervention, post-intervention, and 3-month follow-up. After the follow-up tests were collected, the intervention program was applied to the control group.

Immediate post-intervention assessment showed no significant differences between the experimental and control groups in psychotic symptoms, measured by the positive and negative syndrome scale[89], or social functioning, evaluated through the social functioning assessment scale (SFAS)[90]. Nevertheless, at the three-month follow-up, the experimental group demonstrated significant improvements compared to the control group in both positive symptoms and general psychopathology. Additionally, they exhibited notable gains in SFAS subdimensions, such as self-care, interpersonal relationships, and independent living[7].

The ACT-LCP

Yıldız[91] conducted a systematic review examining the influence of ACT on lifestyle and behavioral changes. The study concluded that ACT could promote health-related changes, including improved weight management, better coping with substance abuse or addictive behaviors, addressing eating problems, and increasing physical activity.

Chong et al[70] conducted a pilot RCT involving 72 EP patients to evaluate the feasibility, acceptability, and effectiveness of the ACT-LCP. Participants were randomly assigned to either the ACT-LCP or active control groups. Those in the ACT-LCP group participated in a five-week group program designed to encourage healthy lifestyle changes based on ACT principles, followed by a reinforcement session, and two telephone follow-ups. The active control group was provided with standard care, a single lifestyle psychoeducation session, and three telephone follow-up sessions. The study outcomes were assessed at baseline, as well as one and 12 weeks after treatment. The authors offered a detailed description of the interventions[70]. Table 7 summarizes the objectives and content covered in each session.

Table 7 Description of the intervention protocol: Acceptance and commitment therapy-based lifestyle counseling program.

Session	Content
Session 1: Commitment, guidance, and psychoeducation in ACT	To provide an overview of ACT and establish goals for adopting healthy lifestyle habits
Session 2: Relationship between a healthy lifestyle and a sense of purpose	To guide participants in identifying their personal values and exploring how they can be aligned with healthy lifestyle choices
Session 3: Acceptance and shared humanity	Decrease fusion between self-criticism and self-concept and cultivate a personal perspective
Session 4: The inevitability of “that”	Implement strategies to manage negative cognitions associated with healthy behaviors
Session 5: Commitment to action	Develop behaviors related to a healthy lifestyle that align with personal values

ACT-LCP: ACT-based lifestyle counseling program[70]. “That” refers to the cognitions and feelings that usually hinder our attempts to engage with our desired healthy behaviors and other values. ACT: Acceptance and commitment therapy.

The results demonstrated significant increases in physical activity levels at the 12-week follow-up for participants in the ACT-LCP group compared to the control group. Furthermore, the ACT-LCP group experienced marked improvements in quality of life, motivation, mental state (psychotic symptoms), and PF[70].

DISCUSSION

To the best of our knowledge, this is the first study to comprehensively review advanced ACT-based interventions for individuals in the early stages of psychosis, making it a pioneering research topic. Only a few studies, primarily published in the last 5 years, have explored the feasibility and efficacy of ACT in EP. Five of them were RCTs with moderate methodological quality.

Their findings suggest that ACT-based treatments show great promise and may contribute to improvements in psychotic symptoms, medication adherence, psychosocial functioning, and a reduction in hospitalizations among patients with EP or FEP.

Furthermore, growing evidence highlights the advantages of group-based interventions, delivered online, as well as hybrid approaches that combine in-person therapy with an EMI method, enabling the application of therapeutic content in real-life scenarios.

Recent studies have highlighted the advantages of incorporating ACT and mindfulness-based therapies for patients with psychosis[3,21,31,92]. Overall, ACTp is recognized as a safe and effective approach for addressing a wide array of therapeutic objectives, such as psychotic symptoms, mood disorders, anxiety, post-traumatic stress, psychosocial functioning, help-seeking behaviors, satisfaction, reduced rehospitalization rates, mindfulness skills, and PF[35,65,93-95]. Similarly, the findings of this review indicate that ACT-based interventions may improve psychotic symptoms, psychosocial functioning, and various other clinical outcomes in patients with EP.

An RCT included in this review demonstrated that an online group ACT-based program led to significant reductions in positive, negative, and general symptoms compared to TAU[7]. Additionally, the ACT group showed higher levels of functioning and fewer hospitalizations[7]. Accordingly, earlier meta-analyses reviewed by Morris et al[21] also emphasized improvements in these outcomes with ACTp. Moreover, these findings hold significant importance, as the results of studies utilizing online formats appear similar to those observed in in-person ACT interventions[3]. In extraordinary circumstances, such as the past coronavirus disease 2019 pandemic, when healthcare services are disrupted and contact patient is limited, online services can serve as a practical alternative, offering both time and cost savings[96,97].

Medication adherence is a critical factor in managing psychotic disorders[98-100]. Nonadherence to antipsychotic medication and a limited understanding of the illness are among the most important preventable causes of relapse[101]. A recent RCT highlighted the effectiveness of an AIM-AT in patients with EP. Participants in the AIM-AT program showed statistically significant improvements in both medication adherence and their understanding of the illness and treatment, compared to those who received only traditional psychoeducation or TAU[69]. The AIM-AT group had better performance regarding psychotic symptoms, psychosocial functioning, service satisfaction, duration of rehospitalizations, and total hospitalizations over the 12-month follow-up. These promising findings from the RCT advocate for incorporating AIM-AT into multicomponent programs within routine clinical practice in community mental health services for adults with EP[69]. Furthermore, they align with earlier evidence supporting the effectiveness of mindfulness-based psychoeducational interventions in patients with FEP[102,103].

Moreover, the latest RCT included in this review revealed that a 5-week group program centered on ACT-LCP was both practical and well-received, suggesting its preliminary effectiveness in individuals with EP[70]. Notable improvements were observed in PF, autonomous motivation, psychotic symptoms, and quality of life[70]. Earlier research has demonstrated the effectiveness of ACT in fostering motivation for behavior changes based on personal values[91,104]. Therefore, ACT-based interventions aimed at young people in the early stages of psychosis have the potential to enhance their self-care abilities and reduce the likelihood of future complications[91].

Importantly, innovative digital interventions, such as EMI, which highlight transdiagnostic mechanisms in everyday life, show promise as translational strategies for preventing and intervening early in psychosis and other severe mental conditions[49,105]. Building on this approach, several studies have shared findings from the multicenter INTERACT study[64]. This RCT investigated the effectiveness of ACT-DL, a hybrid intervention that integrates in-person training sessions with ACT-based EMI delivered via a smartphone app. Early findings revealed that ACT-DL is both feasible and effective, supporting patients in integrating ACT skills into their daily routines[65]. Recent studies have further demonstrated good treatment engagement and acceptance of ACT-DL in EP, demonstrating its successful real-world application and its role in enhancing emotional awareness[68]. Additionally, greater adaptability in emotion regulation has been linked to more stable negative emotions and faster emotional recovery in patients with EP[54].

Regarding efficacy, a preliminary RCT revealed that depressive symptoms were lower among participants in the ACT-DL condition compared to those in the active control group[66]. However, ACT-DL did not enhance PF, which contrasts with the findings of Shi et al[76], who reported improvements in PF following ACT intervention in patients with remitted schizophrenia.

To date, the most comprehensive report based on data from the INTERACT study has provided encouraging evidence for the effectiveness of ACT-DL across different outcomes. This is the largest trial examining ACTp[67]. The ACT-DL group showed significant gains in global functioning, reduced negative symptoms, and decreased momentary psychotic distress when compared to the TAU group. These results could be particularly valuable, as negative symptoms are challenging to treat in early-stage psychosis[106]. Moreover, a qualitative study revealed that participants in the INTERACT study “generally understood and connected with the meaning of ACT, noticing more awareness and acceptance of their thoughts and feelings and living more in line with their personal values”[107].

These findings align with previous research that identified ACT-DL as a feasible mobile health solution for addressing various mental health issues[108]. They also reinforce the potential of internet-based interventions in supporting people with psychosis[109], as well as the role of mixed transdiagnostic interventions in improving sustained engagement and stronger therapeutic alliances[110]. Engagement remains a challenge for traditional psychotherapies; however, the use of certain technological advances has been shown to increase the commitment of young people with EP[111].

Beyond conventional approaches, there is a growing interest in digital and interactive interventions for managing EP[112]. Among these, “Horyzons” was specifically designed to prevent relapse and support recovery in young people with FEP[113]. This web application provides interactive, evidence-based psychosocial interventions and online social networking, moderated by clinicians and peers[113]. Findings from RCTs indicate that “Horyzons” is an effective tool for enhancing social recovery and reducing relapse rates among young people with FEP[114]. Additionally, several studies have highlighted the cost-effectiveness of enhancing social functioning among patients engaged in early intervention programs[115]. Web and mobile apps are emerging as promising tools that can help provide better care, symptom self-management, and coordination of services. However, this new field of research faces multiple challenges, including ethical issues, cost, and healthcare infrastructure capacity, along with concerns with respect to the quality of apps on the market[111]. Moreover, limited economic resources may reduce the benefits of digital approaches to mental healthcare. In addition, the extent to which cognitive deficits, which are often observed in EP, could impact the ability to benefit from these interventions, has not been adequately studied, and the results are inconsistent[116]. Contrary to expectations, Fulford et al[116] found that cognitive performance was not typically correlated with engagement or outcomes in a digital intervention particularly designed for patients with psychosis.

Interestingly, a recent study involving patients from the INTERACT study investigated whether specific neural reactivity patterns are present in patients with EP and how brain activity in these regions correlates with stress reactivity in daily life[117]. Chronic stress in EP patients may be associated with alterations in brain activity within key regions governing emotion regulation and emotional experience, including the limbic system (e.g., hippocampus and amygdala), prelimbic regions (e.g., ventromedial prefrontal and anterior cingulate cortices), and areas related to salience attribution (e.g., anterior insula)[117]. Reininghaus et al[118] identified stress sensitivity, abnormal salience attribution, and threat anticipation as key psychological processes contributing to the occurrence of psychotic experiences in everyday life among EP patients. Therefore, early interventions focused on coping and emotion regulation could lower stress levels and potentially alleviate psychotic symptoms by reducing aberrant salience attribution[118]. ACT enhances PF, enabling individuals to manage stress more effectively and resulting in reduced psychotic symptoms[21]. Therefore, ACT may be a promising approach for the early stages of psychosis[118].

Moreover, several moderators and predictors of clinical outcomes have been identified for EP patients undergoing ACT, with recent studies emphasizing ACT-DL[53,54]. Although ACT-DL enhances clinical outcomes in EP patients, the extent of improvement differs among patients and can be anticipated based on baseline characteristics. If these findings are confirmed, they may have significant clinical implications, contributing to precision medicine approaches that help clinicians select the best candidates and tailor more personalized treatment plans for EP patients[53].

Finally, there have been few studies on the implementation of ACT for EP in routine clinical practice, which hinders its international dissemination relative to other evidence-based therapies, such as the use of CBT for psychosis. Despite ACT’s cross-cultural validity and adoption in different countries and regions, it is not widely included in clinical guidelines. The lack of specific training for clinicians further hinders its implementation. In addition, the similarities between ACT and CBT, which comprise elements such as behavioral activation, mindfulness, acceptance, and values, can create confusion when distinguishing between the two therapies[21]. Possible solutions to overcome these barriers include the development of training and supervision programs to increase clinician capacity for ACT or the adaptation of strategies according to the characteristics of health systems[21]. Furthermore, differences in healthcare systems across countries influence feasibility and implementation of such strategies. For example, clinicians might struggle to integrate ACTp into traditional biomedical models that are focused on symptom reduction in some regions or countries.

Limitations and further research

First, although the methodological quality criteria of the reviewed studies were evaluated, the outcomes have been wide-ranging in different studies, encompassing improvements in symptoms, psychosocial functioning, rehospitalization rates, treatment adherence, and lifestyle. This variability complicates the process of synthesizing these findings into a cohesive framework. Nevertheless, we conducted this review comprehensively and adhered to established guidelines for systematic reviews[62,63]. Additionally, the limited number of available RCTs precluded the possibility of performing a meta-analysis of the results.

While this review primarily concentrated on ACT-based interventions for EP, we also explored a substantial number of studies on ACTp. These studies covered its adaptations, innovations, proposed mechanisms of action, and associated outcomes. This broader exploration provided valuable context and reinforced the findings regarding ACT for EP.

Second, another limitation lies in the methodological challenges of the reviewed studies, such as variations in methods, assessment tools, and relatively small sample sizes. Moreover, active control interventions and TAU are not always well-described and may not be standardized across groups in certain studies. For example, the use of antipsychotics has not been consistent across trials and conditions. This is an important issue because it makes it difficult to clarify the additional effects of medication on ACT effects and vice versa.

Third, the reviewed studies varied in therapeutic formats, encompassing individual, group, online, and hybrid approaches. The interventions themselves also varied considerably, from those that strictly followed the standard ACT model to others incorporating only specific components, such as acceptance or mindfulness. Additionally, some interventions combined ACT elements with other therapies, such as psychoeducation and motivational interviewing. This makes it difficult to determine the therapeutic element responsible for the change.

Finally, therapeutic efficacy often focuses on symptom reduction, which can create discrepancies between the ACT model and research outcomes. It is important to remember that the aim of ACT is to help individuals live a valued life by aligning with what truly matters to them, even amidst challenging internal experiences. Accordingly, the effectiveness of ACT is not evaluated by the extent of symptom alleviation but rather by the success that comes from the clarification and commitment to personal values[119].

Consequently, the results reported by the studies and summarized in this review should be interpreted cautiously and not regarded as definitive recommendations.

Future research, both foundational and clinical, should prioritize exploring effective ways to integrate ACT with existing evidence-based psychopharmacological[120] and psychosocial[121-123] interventions for EP. These include approaches such as CBT, metacognitive training, psychoeducation, family interventions, supported employment, and other evidence-based treatments for psychosis[2]. While the reviewed studies have incorporated innovative real-time digital interventions and explored the practical applications of therapeutic components, future research should aim to refine experimental designs, create novel interventions, identify moderators and predictors of clinical outcomes, deepen understanding of the barriers and facilitators to their implementation in routine clinical settings, and further explore the possibilities offered by new technologies[2].

CONCLUSION

ACT-based interventions aimed at young individuals in the early stages of psychosis are both practical and well-received. Ongoing research is progressing quickly and provides encouraging evidence about the potential of these interventions to alleviate primary symptoms, promote medication adherence, and enhance psychosocial functioning. Additionally, they may foster self-care abilities, including maintaining healthy lifestyles, and help mitigate future complications. Early evidence also highlights the potential advantages of group-based, online-delivered therapies and hybrid approaches that combine in-person sessions with innovative digital methods, such as EMI, to apply therapy in real-life scenarios. While ACT has been of interest for psychotic disorders since its implementation, its use in the early stages of illness is a more recent development. However, controlled studies remain, and the results are inconclusive. Further studies are needed to validate these initial findings and provide more conclusive evidence.