Relation between cannabis use and subcortical volumes in people at clinical high risk of psychosis

Abstract

Among people at genetic risk of schizophrenia, those who use cannabis show smaller thalamic and hippocampal volumes. We evaluated this relationship in people at clinical high risk (CHR) of psychosis. The Alcohol and Drug Use Scale was used to identify 132 CHR cannabis users, the majority of whom were non-dependent cannabis users, 387 CHR non-users, and 204 healthy control non-users, and all participants completed magnetic resonance imaging scans. Volumes of the thalamus, hippocampus and amygdala were extracted with FreeSurfer, and compared across groups. Comparing all CHR participants with healthy control participants revealed no significant differences in volumes of any ROI. However, when comparing CHR users to CHR non-users, a significant ROI × Cannabis group effect emerged: CHR users showed significantly smaller amygdala compared to CHR non-users. However, when limiting analysis to CHR subjects who reported using alcohol at a ‘use without impairment’ severity level, the amygdala effect was non-significant; rather, smaller hippocampal volumes were seen in CHR cannabis users compared to non-users. Controlling statistically for effects of alcohol and tobacco use rendered all results non-significant. These results highlight the importance of controlling for residual confounding effects of other substance use when examining the relationship between cannabis use and neural structure.

Are cannabis-using and non-using patients different groups? Towards understanding the neurobiology of cannabis use in psychotic disorders

“…A number of smaller studies in high-risk samples have supported regional grey matter loss associated with heavier cannabis use (cingulate cortex, prefrontal cortex, cortical thickness) (Habets et al, 2011;Rapp et al, 2013;Stone et al, 2012). In the largest cohort -the North American Prodrome Longitudinal Study (NAPLS) -evaluating clinical high-risk groups there was noted to be no difference between cannabis users (defined as use in the last month) in hippocampal, amygdala, and thalamic volumes and thalamic connectivity, although there was a correlation between younger age of onset and thalamic connectivity with the sensory motor cortex (Buchy et al, 2015(Buchy et al, , 2016.…”

Association between age of cannabis initiation and gray matter covariance networks in recent onset psychosis

“…Cannabis use is associated with structural GM changes in brain regions consistently associated with psychosis [ 8 , 9 ], including the hippocampus, amygdala, as well as striatal, prefrontal cortical, and cerebellar regions [ 5 , 10 ]. These GM alterations can be discerned in cannabis-using patients with psychosis [ 11 ], prodromal individuals [ 12 ] and in healthy individuals who use cannabis regularly [ 13 ].…”

Fronto-temporal cortical grey matter thickness and surface area in the at-risk mental state and recent-onset schizophrenia: a magnetic resonance imaging study

“…Also, cannabis use per se does not appear to be associated with cortical grey matter thinning in people with schizophrenia and bipolar affective disorder whereas cannabis use before the onset of mental illness is associated with reduced caudal middle frontal gyrus after controlling for tobacco and alcohol use disorders [ 28 ]. Buchy et al [ 29 ] reported smaller hippocampal volumes in genetically high-risk individuals consuming cannabis compared to high-risk non-users. This difference became non-significant when controlling for alcohol and tobacco use.…”