ABSTRACT
Objective: Schizophrenia is a multifactorial disorder. It is known that a combination of extensive multiple common alleles may be involved in its etiology, each contributing with a small to moderate effect, and, possibly, some rare alleles with a much larger effect size. We aimed to perform a systematic review of association studies between schizophrenia (and its subphenotypes) and polymorphisms in the CNR1 gene, which encodes cannabinoid receptors classically implicated in schizophrenia pathophysiology, as well as to present unpublished results of an association study in a Brazilian population. Methods: Two reviewers independently searched for eligible studies and extracted outcome data using a structured form. Papers were retrieved from PubMed and ISI Web of Knowledge using the search term schizophrenia in combination with CNR1 or CB1 or cannabinoid receptor. Twenty-four articles met our inclusion criteria. We additionally present data from a study of our own comparing 182 patients with schizophrenia and 244 healthy controls. Results: No consistent evidence is demonstrated. Conclusion: Some seemingly positive association studies stress the need for further investigations of the possible role of endocannabinoid genetics in schizophrenia.
Subject(s)
Humans , Male , Female , Adult , Middle Aged , Schizophrenia/genetics , Polymorphism, Single Nucleotide , Receptor, Cannabinoid, CB1/genetics , Antipsychotic Agents/therapeutic use , Brazil , Case-Control Studies , Comorbidity , Endocannabinoids/genetics , Genetic Association Studies , Gene FrequencyABSTRACT
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.
OBJETIVO: A esquizofrenia é um transtorno psiquiátrico cujos mecanismos permanecem apenas parcialmente elucidados. As atuais propostas relativas à base biológica, tais como a hipótese dopaminérgica, não explicam por completo a diversidade de seus sintomas, o que indica que outros processos podem estar envolvidos. Este artigo tem como objetivo revisar indícios que sustentem o envolvimento do sistema endocanabinoide (SECB), um grupo de neurotransmissoresalvo dos compostos da Cannabis sativa, nesse transtorno. MÉTODOS: Revisão sistemática dos artigos originais, publicados em inglês e indexados no PubMed até abril de 2012. RESULTADOS: A maioria dos estudos empregou métodos neuroquímicos ou de neuroimagem genéticos e histológicos - tanto in vivo quanto post-mortem - para investigar se os componentes do SECB estão comprometidos nos pacientes. De modo geral, os dados mostram mudanças nos receptores canabinoides em determinadas regiões cerebrais, bem como a alteração dos níveis de endocanabinoides no líquido cefalorraquidiano e/ou no sangue. CONCLUSÕES: Ainda que a disfunção do SECB tenha sido descrita, os resultados dos estudos não são totalmente consistentes. São necessários mais dados para definir melhor o papel desse sistema na esquizofrenia.