The Effects of Extended Cannabis Abstinence in Comorbid Posttraumatic Stress Disorder and Cannabis Use Disorder

Objective: This preliminary open-label study examined whether 12 weeks of cannabis abstinence was associated with posttraumatic stress disorder (PTSD) symptom improvement in people with comorbid PTSD and cannabis use disorder (CUD) (N=21).

Methods: Participants received progressive contingency reinforcement payments for successful abstinence at weeks 4, 8, and 12. Abstinence was defined as a 11-nor-9-carboxy-tetrahydrocannabinol (THC-COOH) level ≤50 ng/mL with no self-reported cannabis use. PTSD symptoms were evaluated using the Clinician-Administered PTSD Scale for DSM-5 (CAPS-5), capturing total severity, symptom count, and cluster scores. Data were collected from January 2022 to April 2025.

Results: Participants who achieved abstinence (n=11) reported significantly greater reductions in total PTSD symptom severity and symptom count relative to those who did not (n=10). CAPS-5 total scores decreased from 36.2 to 10.5 among abstainers versus 34.6 to 21.8 among nonabstainers (P=.001). Time-by-group interactions revealed more pronounced improvements in avoidance, negative mood and cognition, and hyperarousal among abstainers. Reexperiencing symptoms improved across both groups over time, with no significant difference by abstinence status.

Conclusions: Sustained cannabis abstinence was associated with significant reductions in PTSD symptom severity and frequency over 12 weeks. While not definitive, the results raise questions about the assumption that long-term cannabis use improves symptoms or functioning in PTSD. The data instead suggest that continued cannabis use could limit recovery in some domains. This underscores the need to routinely assess cannabis use during PTSD treatment and to educate patients on the potential consequences of continued use. Larger randomized trials are warranted to replicate and extend these findings and to investigate mechanisms through which abstinence may relate to symptom changes in PTSD with CUD.

Trial Registration: ClinicalTrials.gov identifier: NCT05162651.