How changes in post-traumatic stress disorder (PTSD) severity mediate substance use disorder (SUD) severity during and after treatment for co-occurring PTSD and SUD: Results from Project Harmony.

BACKGROUND AND AIMS: Post-traumatic stress disorder (PTSD) commonly co-occurs with substance use disorders (SUD). Comorbid PTSD and SUD (PTSD+SUD) is associated with greater severity and impairment and poorer treatment outcomes. Several interventions exist to treat PTSD, SUD and PTSD+SUD; however, research has yet to elucidate the indirect pathways underlying treatment for PTSD+SUD. The present study examined how changes in PTSD severity relate to changes in SUD severity across treatment types during and post-treatment.

METHODS

Observational study using data collected as part of Project Harmony, a virtual clinical trial employing integrative data analysis to compare treatment effectiveness of PTSD+SUD interventions from 36 randomized controlled trials for PTSD+SUD (n = 4046). Multilevel mediated linear growth modeling was used to examine potential outcomes mediation. Each of the eight active treatments was compared to treatment as usual (TAU) for both alcohol and drug use outcomes.

RESULTS

Alcohol use severity outcomes were fully or partially mediated by changes in PTSD severity for trauma-focused psychotherapy + AUD medication [ab = -0.16 (95% confidence interval = -0.30 to -0.04)]; other treatments with mediation effects included trauma-focused integrated psychotherapy, AUD medications and PTSD medications. Drug use severity outcomes were fully or partially mediated by changes in PTSD severity for trauma-focused psychotherapy + AUD medication [ab = -0.08 (-0.18 to -0.001)]; other treatments with mediation effects on drug use severity included trauma-focused integrated psychotherapy, AUD medications, PTSD medications and placebo medications.

CONCLUSIONS

Among people with co-occurring post-traumatic stress disorder (PTSD) and substance use disorders (SUD), reductions in alcohol and drug use severity appear to be mediated by reductions in PTSD during treatment. For those with drug use disorders, PTSD reductions appear to mediate further SUD reductions after treatment.