The most striking finding of this study is the evidence that societal-level protective effects do not extend to individuals with severe mental illness. Specifically, we found that among groups with lower than average rates of substance use (Hispanics and Asians relative to European Americans, and females relative to males), the protective effects of belonging to these groups did not carry over to individuals with severe psychotic disorder: the odds of substance use increased to mitigate the protective effects. For example, relative to non-Hispanic whites, individuals of Hispanic ethnicity have lower rates of heavy alcohol use in controls (5.7% of n=3,424 in Hispanics, 8.1% of n=3,748 in non-Hispanic European Americans, p<0.0001). However, individuals of Hispanic descent with severe psychotic illness have higher rates of heavy alcohol use than non-Hispanic European Americans (28.8% of n=1,583 in Hispanics, 27.3% of n=4,343 in non-Hispanic whites, p=0.001). This highlights the need for targeting substance use specifically among individuals with severe psychotic illness, as protective influences may not carry over from the general population.
