Dietary modification in the treatment of schizophrenia spectrum disorders: A systematic review

Table 1 All included studies

Ref.	Control	Random-ization and Blinding	Population	Sample size	Intervention	Mental health primary outcome	Duration (wk)	Symptom	Direction of Findings
Studies with one or more positive outcomes
Usher et al[17], 2019	TAU	None	Youth, early psychosis	33	Behaviour intervention teaching mindfulness meditation, cooking classes, supermarket trips, fast-food learning, nutrition education, exercise, moderated group discussion to facilitate healthier living	Yes	12	Positive symptoms (Quick Scale for the Assessment of Negative Symptoms)	Improvement
Osborn et al[18], 2018	TAU	Randomized, single blind	Bipolar disorder (50%), schizophrenia (30%) or psychosis (20%); elevated cholesterol and 1 + modifiable risk factors for CVD	327	Manualized intervention to decrease cholesterol and CVD risk: Adherence to statins, improve diet and activity, reduce alcohol, quit smoking	No	52	Psychiatric In-patient costs	Improvement
								QOL (Warwick-Edinburgh Mental Well-being Scale)	Null
Hjorth et al[19], 2017	None	None	Chronic schizophrenia	45	Lifestyle program including nutrition, meal planning, walking/running group, smoking cessation, MI. individual and group components	No	120	QOL (WHOQoL)	Null
			Newly diagnosed schizophrenia	123				QOL (WHOQoL)	Improvement
Juel et al[20], 2017	None	None	Psychotic disorder, affective disorder, anxiety disorder, or developmental disorder with comorbid substance use or dependence; 12.5% SSD	64	Nutrition, exercise and smoking cessation program. Includes health diet habits, reading nutrition labels, macronutrient recommendations. Includes individual and group components	No	24	QOL (WHOQoL)	Improvement
								Medication Usage	Worsening
Masa-Font et al[21], 2015	TAU	None	Schizophrenic, schizoaffective or bipolar, treated with antipsychotic drug (67% SSD); BMI > 25	332	Group nutrition education and exercise sessions	No	12	QOL (SF-36)	Improvement
Farhat et al[22], 2016	None	None	Schizophrenia	8	Group educational program including nutritional balance, meal planning, budgeting, meal preparation, socialization	Yes	16	Negative (PANSS)	Improvement
								Cognitive (BECS)	Null
Provencher et al[23], 2016	Waitlist	None	SMI including psychotic disorders; weight concern	47	Program teaching nutrition and cooking	No	12	QOL	Improvement
Sauvanaud et al[24], 2016	None	None	Schizophrenia	14	Group educational program/ psychosocial program including schizophrenic disease, treatments, relationships to family, diet, social issues, relaxation	Yes	15	Functioning (GAF)	Improvement
								QOL (SQoL)	Improvement
								Medication Adherence (MARS)	Improvement
								Insight (French IQ8)	Null
Stiekema et al[25], 2014	TAU	Treatment centers randomized	Patients with severe mental illness (primarily SSD), inpatient	130	Group diet and exercise intervention: Lifestyle intervention to change the obesogenic environment within residential setting (e.g., Whole grain bread available)	No	12	Depression	Improvement
								Psychological functioning	Improvement
								QOL	Worsening
Robertson et al[26], 2014	None	None	Schizophrenia-spectrum	25	Group healthy lifestyle group, walking group, grocery shopping	Yes	12	Psychotic symptoms (PANSS)	Improvement
Bralet et al[27], 2013	None	None	Schizophrenia	10	Group nutrition education, cognitive remediation, social skills, meal preparation	Yes	17	Psychotic symptoms (PANSS)	Improvement
								Self Esteem	Improvement
								Cognition (BACS, STICCS)	Improvement
Kuo et al[28], 2012	TAU	None	Schizophrenia	63	Group weight reduction program including food recommendations (more vegetables and monounsat fats, less sugar and calories), exercise, behaviour therapy	Yes	10	Biologic (BDNF)	Improvement
								Psychotic symptoms (BPRS)	Null
Porsdal et al[29], 2010	TAU	None	Schizophrenia or bipolar I, taking psychotropic medication	373	Group nutrition and exercise program	Yes	12	QOL (15D)	Null
								Psychotic symptoms (CGI-S)	Improvement
Van Citters et al[30], 2010	None	None	DMS-IV Axis I or II diagnosis; 18% SSD	76	Individualized health promotion program: health eating, exercise social inclusion, decrease calories. Includes individual and group components	No	36	Mental health functioning (SF-12)	Improvement
								Negative symptoms (SANS)	Improvement
Gretchen-Doorly et al[31], 2009	None	None	Schizophrenia	9	Nutrition (avoid high fat food, increase fiber, strategies for weight loss), exercise and stress management coaching	Yes	6	Self-efficacy for health practices, psychological wellbeing, health responsibility	Improvement
Castiglioni et al[32], 2008	Monthly clinical exam	None	Psychotic disorders	26	Group health and Wellness program	No	24	QOL (Quality of Life Index)	Improvement
Guimarães et al[33], 2008	TAU	None	Schizophrenia	67	Calorie-restricted diet; reduction in saturated fat and sugar, increase in fruit and vegetables. Individual delivery	No	4	BDNF	Improvement
Raine et al[34], 2003	TAU	Randomized	Children aged 3-5 years, no diagnosis	438	Group nutrition, education and physical exercise program: structured nutrition program provided the children with milk, fruit juice, a hot meal of fish or chicken or mutton, and a salad each day	Yes	104	positive schizotypal personality (Schizotypal personality questionnaire)	Improvement
								Cognition (Schizotypal personality questionnaire)	Improvement
Aquila et al[35], 2000	None	None	Inpatients with severe persistent mental illness taking atypical antipsychotics	32	Group diet intervention to decrease fat, calories, sugar, snacking	No	78	Negative (subjective assessment)	Improvement
Studies without positive outcomes
Holt et al[36], 2019	TAU	Randomization	Schizophrenia, schizoaffective disorder or first-episode psychosis, antipsychotic medication, BMI > 25 or concern about weight	412	Education on nutrition, physical activity and weight management. individual and group components	No	40	Depression	Null
								Psychotic symptoms (BPRS)	Null
Stiekema et al[37], 2018	TAU	Randomized, Blinded	Psychotic disorder, mood disorder, personality disorder, anxiety, substance use disorder, developmental disorder or psychiatric comorbidity; 74% SSD; inpatient	770	Diet and exercise lifestyle intervention to adjust obesogenic environment (offer low-fat cheese, whole wheat alternatives, less sweets, smaller portions of snacks, fresh rather than canned vegetables) Includes individual and group components	Yes	52	Psychotic symptoms (PANSS)	Null
								QOL (MANSA)	Worsening
								Depression (CDSS)	Null
Naslundet al[38], 2017	Gym membership	Randomized	Major depressive disorder, schizoaffective disorder, or schizophrenia; 46% SSD	343	Individual nutrition, MI, fitness goal setting	Yes	52	Depressive Symptoms (CESD)	Null
Detke et al[39], 2016	Single 15-min session of basic information	None	Schizophrenia or Bipolar I	203	Individual intense behavioural weight counseling – nutrition education, pedometer, motivational enhancement, guidance on caloric restriction, low-fat, nutrient dense foods in moderate portion sizes	No	52	Psychotic symptoms (BPRS-C)	Null
Speyer et al[40], 2016	TAU	Randomized, blinded	Schizophrenia, schizoaffective disorder or persistent delusional disorder, abdominal obesity	428	Individual lifestyle program teaching healthy diet, cooking, smoking cessation, physical activity, coordination of care for somatic health	No	52	Psychotic symptoms (SANS and SAPS)	Null
								Perceived health and stress	Null
								Cognition (BACS)	Null
								QOL (MANSA/Euro QoL)	Null
Jones et al[41], 2007	None	None	Taking antipsychotic medication	50	Group psychoeducation and physical activity program including nutrition, budgeting, cooking, goal setting	No	10	QOL (SF-36)	Null

BACS: Brief Assessment of Cognition in Schizophrenia; BDNF: Brain-derived neurotrophic factor; BMI: Body mass index; BPRS: Brief psychiatric rating scale; CDSS: The Calgary Depression Scale for Schizophrenia; CESD: Center for Epidemiological Studies Depression scale; CVD: Cardiovascular disease; GAF: Global Assessment of Functioning; MANSA: Manchester Short Assessment of Quality of Life; MARS: Medication Adherence Rating Scale; MI: Motivational interviewing; PANSS: The Positive and Negative Syndrome Scale; QOL: Quality of life; SANS: Scale for the Assessment of Negative Symptoms; SAPS: Scale for the Assessment of Positive Symptoms; SF-12: 12-Item Short Form Health Survey; SF-36: The 36-Item Short Form Health Survey questionnaire; SMI: Severe mental illness; SSD: Schizophrenia spectrum disorders; STICCS: Subjective Scale to Investigate Cognition in Schizophrenia; TAU: Treatment as usual; WHOQoL: World Health Organization Quality of Life –Brief.

Table 2 Characteristics of studies that reported benefit in mental health outcomes and those that did not

	Number of studies reporting benefit (%)	Number of studies not reporting benefit (%)	P value
Studies with greater than 200 participants	4 of 19 (21)	5 of 6 (83)	0.00559
Studies that included patients with non-SSD diagnoses (e.g., Depression, Bipolar, substance use disorder)	8 of 19 (42)	4 of 6 (67)	0.29380
Studies with an individual intervention component	2 of 19 (11)	3 of 6 (50)	0.03509
Studies designed with primary outcome related to mental health	9 of 19 (47)	2 of 6 (33)	0.54599
Studies that used a control	10 of 19 (53)	5 of 6 (83)	0.18081
Studies that used randomization	3 of 19 (16)	4 of 6 (67)	0.01553
Studies with positive finding in an outcome related to body weight	7 of 10 (70)	1 of 4 (25)	0.12428