Schizophrenia, substance use, and brain morphology.

The high rate of comorbid substance abuse in schizophrenia and the consistently poor outcome of this comorbidity are well established findings in the research literature. However, the reasons for the high rate of comorbidity are not adequately understood, and the question of why some patients with schizophrenia abuse substances and others do not remains unanswered. There is widespread agreement about the clinical heterogeneity of schizophrenia, and there is some evidence suggesting that the heterogeneous clinical presentation may reflect a parallel underlying heterogeneity of brain morphology. We were interested in examining the possibility that the high rate of substance abuse and the characteristically poor outcome may be associated with the underlying brain morphology. Our hypothesis was that study subjects with schizophrenia and substance abuse would have higher rates of gross brain abnormalities than subjects with only schizophrenia. In an attempt to explore this possibility, we looked at qualitative differences in magnetic resonance imaging scans for a large sample (n = 176) of schizophrenia patients. In the group of patients who abused both alcohol and drugs, we found the rate of gross brain abnormalities to be slightly less than half the rate found among the patients with no history of alcohol or substance abuse (8 vs. 19). Although these results are not statistically significant, they reflect a trend that is compatible with previous findings, suggesting that substance abuse history may be accompanied by less impairment in certain areas, which in turn may be reflected in a better premorbid adjustment. However, our findings are not compatible with previous findings that show substance abuse to be associated with more severe symptoms and a poorer outcome in schizophrenia.