Abstract
Posttraumatic stress disorder (PTSD) symptoms and alcohol use frequently co-occur and are mutually reinforcing. Few studies have examined how changes in PTSD severity influence subsequent changes in alcohol use, particularly in the context of comorbidity treatments. This secondary analysis utilized data from a clinical trial comparing 12 weeks of Seeking Safety plus sertraline (SS+S) versus Seeking Safety plus placebo (SS+P) among individuals (N = 69) with co-occurring PTSD and alcohol use disorder. A mediational analysis, using a latent growth modeling framework from five points throughout treatment, was conducted to examine whether reductions in alcohol use were mediated by treatment-led (SS+S vs. SS+P) reductions in PTSD severity. Results revealed a nonsignificant treatment effect on PTSD severity reductions over time, Est. = −0.440. The link between PTSD severity reductions and reductions in alcohol use was significant, Est. = 0.644. Despite the nonsignificant path between treatment group and PTSD severity (and in the presence of bias correction for small sample size), the formal test of mediation was significant such that for participants in the SS+S group, alcohol use reductions were fully mediated by reductions in PTSD severity, Est. = −0.283. These findings suggest one of the mechanisms through which SS+S exerts its effects on alcohol use is through reductions in PTSD severity. Clinicians working within the SS treatment platform may consider augmenting their treatment plan with sertraline in collaboration with clients. Future research is necessary to understand how medication and behavioral therapies synergize over a treatment course to improve PTSD and alcohol use.