Objective: The present study investigated predictors of treatment attendance among 226 women with posttraumatic stress disorder (PTSD) and substance use disorder (SUD). Participants received either an integrated intervention for PTSD and SUD ("Seeking Safety") or a relapse prevention training (RPT) as part of a multicenter randomized controlled trial. Method: Beta-binomial regression was conducted to investigate baseline sociodemographic, motivational, mental health and substance use predictors of session attendance. Treatment by predictor interactions were included to identify treatment-specific predictors. Results: Session attendance was predicted by employment status, drug use severity and abstinence status. Higher drug use severity and unemployment were associated with less session attendance. The effect of abstinence status was treatment-specific, with abstinent participants in RPT attending most sessions. Conclusions: Considering individual characteristics could enhance session attendance in outpatient treatment for women with PTSD and SUD. This might include matching treatment concepts to abstinence status, the identification of attendance barriers in unemployed women and more intensive treatment settings for those with severe drug use.
