Cannabis use, cognition and brain structure in first-episode psychosis

 The use of cannabis is widespread and has been associated with the development of schizophrenia and psychosis, especially when used by teenagers. This link, however, remains controversial, and the results of various studies have been inconclusive and varied. A study published in the scholarly journal Schizophrenia Research aims to investigate the relationship between brain structure in psychotic patients and prior cannabis use. 200 patients with first-episode psychosis were selected from an epidemiological study on the incidence of psychotic disorders in São Paulo, Brazil. The patients were screened for contraindications for MRI scanning, head injury, substance-induced psychosis, and other potentially confounding factors. The remaining suspects were divided into two groups, based on whether they had previously used cannabis or not. 80 individuals from the same catchment area with no history of cannabis use or psychosis were recruited as controls. The subjects underwent an MRI scan and a series of tests to measure cognitive function. The MRI scan examined gray matter and lateral ventriclevolumes.

The analysis showed that psychotic patients who had previously used cannabis exhibited less cognitive impairment and fewer structural brain abnormalities than those with no prior history of cannabis use. Additionally, this difference could not be attributed to a difference in the severity of symptoms between the two groups. The researchers hypothesize that exposure to cannabis might be a contributing factor in the development of psychosis in individuals without structural abnormalities, that the subjects in the study may represent two subgroups of psychosis patients, with a different progression of neurodevelopment impairment. Further research is required to examine genetic and environmental factors contributing to psychosis in order to better understand the effect of cannabis on these disorders.

Paulo Jannuzzi Cunha, Pedro Gomes P. Rosa, Adriana de Mello Ayres, Fábio L.S. Duran, Luciana C. Santos, Marcia Scazufca, Paulo R. Menezes, Bernardo dos Santos, Robin M. Murray, José Alexandre S. Crippa, Geraldo F. Busatto, Maristela S. Schaufelberger

Cannabis use, cognition and brain structure in first-episode psychosis 

Schizophrenia Research, Available online 11 May 2013

http://www.sciencedirect.com/science/article/pii/S0920996413002090