Cannabis abuse and brain morphology in schizophrenia: a review of the available evidence

Berend Malchow,Peter Falkai,Alkomiet Hasan,Paolo Fusar-Poli,Thomas Wobrock,Andrea Schmitt

doi:10.1007/s00406-012-0346-3

Abstract

Substance abuse is the most prevalent comorbid psychiatric condition associated with schizophrenia, and cannabis is the illicit drug most often abused. Apart from worsening the course of schizophrenia, frequent cannabis use especially at an early age seems to be an important risk factor for developing schizophrenia. Although a large body of neuroimaging studies gives evidence for structural alterations in many different brain regions in schizophrenia patients, there is still limited knowledge of the impact of cannabis abuse on brain structure in schizophrenia. We performed a systematic review including structural magnetic resonance imaging studies comparing high-risk and schizophrenia patients with and without cannabis abuse and found inconclusive results. While there is some evidence that chronic cannabis abuse could alter brain morphology in schizophrenia in patients continuing their cannabis consumption, there is no convincing evidence that this alteration takes place before the onset of schizophrenia when looking at first-episode patients. There is some weak evidence that cannabis abuse could affect brain structures in high-risk subjects, but replication of these studies is needed.

Highlights

Substance abuse in individuals with schizophrenia is very common; it has become the most prevalent comorbid psychiatric condition associated with schizophrenia and contributes to an unfavourable disease course [65]
While there is some evidence that chronic cannabis abuse could alter brain morphology in schizophrenia in patients continuing their cannabis consumption, there is no convincing evidence that this alteration takes place before the onset of schizophrenia when looking at first-episode
To achieve a comprehensive overview of the available neuroimaging studies dealing with our topic, a systematic literature search and study evaluation were performed according to the CochraneCriteria, using the computerized search databases PubMed (1966–2012) and the Web Of Knowledge

Summary

Introduction

Substance abuse in individuals with schizophrenia is very common; it has become the most prevalent comorbid psychiatric condition associated with schizophrenia and contributes to an unfavourable disease course [65]. Apart from the legal substances such as tobacco and alcohol, cannabis is the most illicit drug abused in schizophrenia patients. In a population-based study, the prevalence of substance use disorder in patients with schizophrenia was estimated to be 4.6 times higher than in the general population [46]. Especially cannabis, has been discussed as an important risk factor for developing schizophrenia [34]. At least substance abuse may contribute to an earlier onset of schizophrenia as seen in many first-episode studies [6]

Methods

Discussion

Conclusion