Effects of psychoactive substances in schizophrenia -- findings of structural and functional neuroimaging

Schizophrenia is a major mental illness that is characterized by psychosis, social withdrawal, and cognitive impairment. High comorbidity rates with substance use disorders have consistently been found - especially with abuse of cannabis and psychostimulants. While the role of these drugs in the onset of psychosis and schizophrenia has received much attention, relatively few studies have been conducted on the impact of psychoactive substances on the course of schizophrenia. In this review, study findings measuring the effects of psychoactive substances with structural and functional magnetic resonance imaging methods are described in patients suffering from substance use disorder and schizophrenia. Both Schizophrenia and substance abuse are associated with different functional brain alterations. In addicted individuals, drug-related cues and drug administration lead to increased neurofunctional activity in limbic and prefrontal brain regions compared to healthy controls. Chronic drug abuse is associated with gray matter loss in these areas. In schizophrenic patients, cognitive imaging in the frontal and temporal brain areas has showed decreased neural activity during the resting state. In chronic schizophrenic patients, the greatest loss of brain volume was found in those patients with additional substance abuse. Neuroimaging studies highlight the significance of regular drug use in schizophrenia. Whereas schizophrenic patients with and without substance abuse may not differ in structural imaging at the onset of illness, regular drug abuse seems to be a significant risk factor for severe loss of brain volume in the course of schizophrenia.