Previous research investigating the etiology of psychosis has identified risk factors such as childhood sexual abuse and cannabis use. This study investigated the multiplicative effect of these variables on clinically assessed diagnoses of psychosis based on a large community sample (the National Comorbidity Survey). Demographic variables (sex, age, urbanicity, ethnicity, education, employment, and living arrangements) and depression were used as predictors in the first block of a binary logistic regression. In the second block, the variables representing early cannabis use, childhood sexual trauma, and the interaction between these variables were entered. There was no significant main effect for early cannabis use or childhood sexual trauma. The interaction was statistically significant (odds ratio [OR] = 6.93, 95% confidence interval [CI] = 1.39-34.63, P = .02). The effect for the sexual trauma variable was statistically significant for those who used cannabis under 16 years (OR = 11.96, 95% CI = 2.10-68.22, P = .01) but not for those who had not used cannabis under 16 years (OR = 1.80, 95% CI = 0.91-3.57, P = .09). Many factors have been shown to be significant in the etiology of psychosis; however, the current research augments previous findings by examining psychosis in terms of an interaction between 2 of these factors.