The endocannabinoid system and its role in schizophrenia: a systematic review of the literature

Objective: Schizophrenia is a psychiatric disorder whose mechanisms have remained only partially elucidated. The current proposals regarding its biological basis, such as the dopaminergic hypothesis, do not fully explain the diversity of its symptoms, indicating that other processes may be involved. This paper aims to review evidence supporting the involvement of the endocannabinoid system (ECS), a neurotransmitter group that is the target of Cannabis sativa compounds, in this disorder. Methods: A systematic review of original papers, published in English, indexed in PubMed up to April, 2012. Results: Most studies employed genetics and histological, neuroimaging or neurochemical methods - either in vivo or post-mortem - to investigate whether components of the ECS are compromised in patients. Overall, the data show changes in cannabinoid receptors in certain brain regions as well as altered levels in endocannabinoid levels in cerebrospinal fluid and/or blood. Conclusions: Although a dysfunction of the ECS has been described, results are not entirely consistent across studies. Further data are warrant to better define a role of this system in schizophrenia.