Eleven studies of 2,873 predominantly hospital-based psychiatric patients in New York City, Baltimore, and Columbia, South Carolina, indicate the average HIV infection rate among adults with severe mental illness is 7.8 percent (
+2), nearly 20 times the rate of .4 percent estimated for the general population (
+3). Across studies, psychiatric patients with identified comorbid alcohol or other drug use disorders have a significantly higher rate of infection than those without (χ
2 =47.56, df=9, p<.001) (see
+Figure 1). Among patients treated on dual diagnosis units, HIV seroprevalence is significantly related to type of substance used (χ
2 =8.82, df=2, p<.03) (see
+Figure 2).