Abstract
Background: Substance use disorders are frequent among schizophrenia patients. Growing evidence shows that the relationships between substance abuse and psychosis are complex. Substance abuse in schizophrenia is associated with increased positive and depressive symptoms. However, emerging data also shows that substance-abusing schizophrenia patients have fewer negative symptoms, compared to abstinent patients, and that they have fewer cognitive deficits when they are young. Here, our objective is to determine if brain imaging studies conducted among dual-diagnosis schizophrenia patients reflect the paradoxical nature of the relationships between psychosis and addiction. Methods: A systematic search of the literature was performed, and we identified 21 brain imaging studies carried out among substance-abusing patients with schizophrenia. Results: Some studies showed that alcohol and cannabis amplify the anatomic abnormalities of schizophrenia, especially in the cerebellum. However, preliminary functional imaging data from our group highlighted a relative preservation of the medial prefrontal cortex functioning among dual-diagnosis patients during emotional processing. Conclusion: Brain imaging studies performed so far reflect the complex nature of the relationships between psychosis and addiction. Further brain imaging studies involving dual-diagnosis schizophrenia patients are required. Future studies will need to pay attention to length of substance abuse, psychiatric symptoms, antipsychotics, types of psychoactive substances (e.g. cocaine) and the brain reward system.
Keywords: Schizophrenia, substance abuse, functional brain imaging, anatomic imaging
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