PTSD may amplify the risks of drinking alone, but not cannabis use

A substantial proportion of young adults experience alcohol- and cannabis-related consequences. One potential contributor to negative consequences of substance use is context; for example, solitary substance use, which may be more common for those who are experiencing mental health symptoms, such as symptoms of posttraumatic stress disorder (PTSD). This study hypothesized that PTSD symptoms would moderate associations between solitary substance use and consequences for both (a) alcohol and (b) cannabis use. This was secondary data analysis examining young adults across the United States (N = 371; 53.9% male; 56.9% White) who completed an online survey from remote locations assessing alcohol use, cannabis use, frequency of using alcohol and cannabis alone, substance-related consequences, PTSD symptoms, and demographic information. Those reporting alcohol (n = 281) and cannabis use (n = 222) in the past year were included in moderation models. Moderation was tested using negative binomial regression with follow-up tests of simple slopes at high (+1 SD) and low (-1 SD) levels of PTSD symptoms. There was a significant interaction between PTSD symptoms and solitary drinking in the prediction of alcohol-related consequences. Solitary drinking was associated with more alcohol-related consequences only among those reporting high (not low) symptoms of PTSD (incidence rate ratio = 1.01, p = .01, 95% CI [1.00, 1.02]). There was no interaction between PTSD and solitary cannabis use in the prediction of cannabis-related consequences. PTSD symptoms may exacerbate the association between solitary drinking and alcohol-related consequences. Prevention and intervention strategies focused on healthy coping skills may be especially important for those experiencing PTSD symptoms. (PsycInfo Database Record (c) 2026 APA, all rights reserved).