Cannabis use and brain structural alterations of the cingulate cortex in early psychosis (original) (raw)

As cannabis use is more frequent in psychosis patients than the general population and is known to be a risk factor for psychosis, the question arises whether cannabis contributes to recently detected brain volume reductions in schizophrenic psychoses. This study is the first to investigate how cannabis use is related to cingulum volume, a brain region involved in the pathogenesis of schizophrenia, in a sample of both at risk mental state (ARMS) and first episode psychosis (FEP) subjects. A cross-sectional MRI study of manually traced cingulum in 23 FEP and 37 ARMS subjects was performed. Cannabis use was assessed with the Basel Interview for Psychosis. By using repeated measures ANCOVAs, we investigated whether current cannabis use is associated with cingulum volume, correcting for age, gender, alcohol consumption, whole brain volume and antipsychotic medication. There was a significant three way interaction between region (anterior/posterior cingulum), hemisphere (left/right cingulum) and cannabis use (yes/no) (F (1, 51) = 5.62, Partial η 2 = 0.10, p = 0.022). Post hoc analyses revealed that this was due to a significant negative effect of cannabis use (F (1, 51) = 8.96, Partial η 2 = 0.15, p = 0.004) on volume of the posterior cingulum which was independent of the hemisphere and diagnostic group and all other covariates we controlled for. In the anterior cingulum, we found a significant negative effect only on left hemisphere (F (1, 51) = 7.02, Partial η 2 = 0.12, p = 0.011), which was again independent of diagnostic group. Overall, we found negative associations of current cannabis use with grey matter volume of cingulate cortex, a region rich in CB1 receptors. As this finding has not been consistently found in healthy controls, this might suggest that both ARMS and FEP subjects might be particularly sensitive to exogenous activation of these receptors.