Key Takeaways
Extended Takeaways
- Only 11 of 21 completers (52.4%) achieved 12 weeks of biochemically verified abstinence, highlighting that sustained cessation was feasible for about half of this comorbid PTSD/CUD sample under weekly monitoring, brief therapy, and contingency management.
- The separation in PTSD outcomes was clinically large by week 12: CAPS-5 total scores fell from 36.2 to 10.5 in abstinent participants versus 34.6 to 21.8 in nonabstainers, and symptom counts fell from 14.3 to 4.1 versus 13.5 to 8.9.
- Symptom gains were not uniform across PTSD domains; abstinence-related interactions were significant for avoidance and hyperarousal severity (Cluster C: β=−2.34, 95% CI: −3.88 to −0.80, P=.0043; Cluster E: β=−5.57, 95% CI: −8.74 to −2.41, P=.001), which may help target counseling toward symptoms patients often self-medicate with cannabis.
- Reexperiencing symptoms may be less sensitive to cannabis abstinence alone in the short term, as Cluster B showed no significant time×group interaction for symptom count (β=−0.78, 95% CI: −2.02 to 0.47, P=.23) despite overall improvement over time.
- Baseline THC-COOH was not significantly correlated with baseline PTSD burden, and adding THC-COOH as a covariate did not eliminate the abstinence effect on PTSD severity or symptom count, suggesting that sustained abstinence status carried more explanatory value than metabolite level alone in this study.
- Because analyses were restricted to completers and all participants received weekly 20-minute therapy sessions plus abstinence-contingent payments of $200, $300, and $400 at weeks 4, 8, and 12, these findings are most applicable to structured treatment settings rather than usual care without reinforcement.
