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World J Psychiatr. Mar 22, 2015; 5(1): 47-55
Published online Mar 22, 2015. doi: 10.5498/wjp.v5.i1.47
Raising attention to attention deficit hyperactivity disorder in schizophrenia
Stefano Pallanti, Luana Salerno
Stefano Pallanti, Luana Salerno, Istituto di Neuroscienze, 50134 Florence, Italy
Stefano Pallanti, Department of Psychiatry and Behavioral Sciences, University of California, Sacramento, CA 95817, United States
Author contributions: Pallanti S and Salerno L equally contributed to this paper.
Conflict-of-interest: We have read and understood WJP policy on declaration of interests and declare that we have no competing interests.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See:
Correspondence to: Stefano Pallanti, MD, PhD, Istituto di Neuroscienze, Via Lamarmora, 24, 50134 Florence, Italy.
Telephone: +39-55-7949707 Fax: +39-55-581051
Received: October 6, 2014
Peer-review started: October 8, 2014
First decision: November 14, 2014
Revised: November 20, 2014
Accepted: December 29, 2014
Article in press: December 31, 2014
Published online: March 22, 2015

Schizophrenia and attention deficit hyperactivity disorder (ADHD) are two psychiatric disorders with a negative impact on quality of life of individuals affected. Although they are classified into distinct disorders categories, attentional dysfunction is considered as a core feature in both conditions, either at the clinical then pathophysiological level. Beyond the obvious clinical overlap between these disorders, the Research Domain Criteria approach might offer an interesting perspective for disentangling common circuits underpinning both disorders. Hence, we review evidences regarding the overlap between schizophrenia and ADHD, at the clinical level, and at the level of underlying brain mechanisms. The evidence regarding the influence of environmental risk factors in the emergence of both disorders, and their developmental trajectories is also reviewed. Among these, we will try to elucidate the complex relationship between stimulants use and psychotic symptoms, discussing the potential role of ADHD medication in inducing psychosis or in exacerbating it. We aim that, taken together, these findings may promote further investigation with important implications both for clinicians and research. In fact, considering the amounting evidence on the overlap between schizophrenia and ADHD, the delineation of their boundaries might help in the decision for diagnosis and treatment. Moreover, it may help to promote interventions focused on the prevention of both schizophrenia and ADHD, by the reduction of recognized environmental risk factors.

Keywords: Attention deficit disorder with hyperactivity, Central nervous system stimulants, Psychotic disorders, Schizophrenia, Toxic psychoses

Core tip: In line with the translational approach of viewing disorders in terms of dysregulation of brain basic mechanisms, there is increasing evidence of overlap between different mental disorders. Here, we explore relationships between attention deficit hyperactivity disorder and schizophrenia, in light of recent insights into potential common etiological mechanisms explaining some of the observed overlap in both disorders. Using evidence from clinical epidemiology and neuropsychology, we propose a biologically-based reconsideration of these brain diseases. We have also summarized environmental risk factors for both disorders, aiming to promote awareness regarding the need of appropriate interventions to prevent the onset and development of these diseases.