Abstract
It is unclear yet whether cannabis use is a moderating or causal factor contributing to grey matter alterations in schizophrenia and the development of psychotic symptoms. We therefore systematically reviewed structural brain imaging and post mortem studies addressing the effects of cannabis use on brain structure in psychosis. Studies with schizophrenia (SCZ) and first episode psychosis (FEP) patients as well as individuals at genetic (GHR) or clinical high risk for psychosis (ARMS) were included. We identified 15 structural magnetic resonance imaging (MRI) (12 cross sectional / 3 longitudinal) and 4 post mortem studies. The total number of subjects encompassed 601 schizophrenia or first episode psychosis patients, 255 individuals at clinical or genetic high risk for psychosis and 397 healthy controls. We found evidence for consistent brain structural abnormalities in cannabinoid 1 (CB1) receptor enhanced brain areas as the cingulate and prefrontal cortices and the cerebellum. As these effects have not consistently been reported in studies examining non-psychotic and healthy samples, psychosis patients and subjects at risk for psychosis might be particularly vulnerable to brain volume loss due to cannabis exposure
Highlights
Cannabis is the world’s most widely used illicit drug with about 10% of young adults in developed countries being regular users
Functional studies were not considered in this review because we aimed to look for effects of cannabis on brain structure
SCZ showed an increase in the density of [3H]CP-55940 binding in the dorsolateral prefrontal cortext compared to healthy controls (HC)
Summary
Cannabis is the world’s most widely used illicit drug with about 10% of young adults in developed countries being regular users. A neurotoxic effect (e.g. shrinkage of neuronal cell bodies and nuclei) of cannabis in animals has been confirmed in many cases [11, 12]. It is assumed, that 9-tetrahydrocannabinol (THC), the main psychoactive substance in cannabis, is the neurotoxic substance [13]. The effects of cannabis on brain structure and function are of particular interest in psychosis patients, as cannabis is known to be a risk factor for psychosis [14,15,16] and is widely used in patients with psychosis [17]. Cannabis use may be a moderating or causal factor contributing to grey matter alterations in schizophrenia and the development of psychotic symptoms
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