Frequently Asked Questions

In this 12-week study, sustained cannabis abstinence was associated with greater improvement in PTSD symptoms than nonabstinence in people with comorbid PTSD and cannabis use disorder. Among the 21 participants who completed all visits, 11 (52.4%) achieved biochemically verified abstinence. CAPS-5 total PTSD severity fell from 36.2 to 10.5 in abstinent participants versus 34.6 to 21.8 in nonabstinent participants, with a significant time-by-group interaction (β=-12.83, 95% CI: -19.98 to -5.67, P=.001).

Yes. Participants who remained abstinent for 12 weeks had larger reductions in the number of PTSD symptoms meeting CAPS-5 threshold than those who did not remain abstinent. Total symptom count decreased from 14.3 to 4.1 in the abstinent group versus 13.5 to 8.9 in the nonabstinent group, with a significant time-by-group interaction of β=-5.59 (95% CI: -8.79 to -2.40, P=.001).

The clearest abstinence-associated differences were seen in avoidance and hyperarousal symptoms. For CAPS-5 cluster severity, significant time-by-group interactions were found for Cluster C avoidance (β=-2.34, 95% CI: -3.88 to -0.80, P=.0043) and Cluster E hyperarousal (β=-5.57, 95% CI: -8.74 to -2.41, P=.001).

For symptom counts, significant interactions were found for Cluster C avoidance (β=-0.88, 95% CI: -1.58 to -0.17, P=.018), Cluster D negative alterations in cognition and mood (β=-2.33, 95% CI: -4.39 to -0.28, P=.03), and Cluster E hyperarousal (β=-2.51, 95% CI: -3.75 to -1.26, P<.001).

Not clearly. The study found no significant time-by-group interaction for Cluster B reexperiencing symptom count (β=-0.78, 95% CI: -2.02 to 0.47, P=.23), which suggests abstinent and nonabstinent participants did not differ significantly on that measure. The authors noted that both groups showed some Cluster B improvement over time, and they suggested this could reflect factors unrelated to cannabis abstinence or limited statistical power.

Participants were classified as continuously abstinent only if they self-reported no cannabis use from baseline through week 12 and had urine THC-COOH levels of 50 ng/mL or lower at weeks 4, 8, and 12. Anyone who reported cannabis use or had THC-COOH levels above 50 ng/mL at any of those timepoints was classified as nonabstinent.

Abstinence was assessed with Timeline Followback self-report and verified with semi-quantitative urine THC-COOH testing collected at baseline and weeks 1, 2, 3, 4, 8, and 12.

Among the 21 participants with complete data, 11 participants (52.4%) achieved 12 weeks of biochemically verified cannabis abstinence. The analysis was limited to completers because abstinence status required biochemical verification across all study timepoints.

No. In exploratory mixed-effects models that added urine THC-COOH concentration as a covariate, THC concentration was not a significant predictor of PTSD severity, and the time-by-abstinence interaction remained significant after adjustment (P=.03). The same pattern was reported for total PTSD symptom count, where the abstinence interaction remained significant after controlling for THC-COOH (P=.026).

This was a prospective 12-week study in adults aged 18 to 65 years with DSM-5 PTSD and current cannabis use disorder. Participants were asked to stop cannabis use, and PTSD symptoms were measured at baseline and at weeks 4, 8, and 12 using the CAPS-5.

All participants received weekly study visits, urinalysis, and motivational interviewing sessions. They also received brief 20-minute weekly individual therapy sessions between weeks 1 and 4 that combined psychoeducation, motivational interviewing, and coping skills therapy. Participants who achieved abstinence at weeks 4, 8, and 12 were eligible for contingent cash bonuses of $200, $300, and $400, respectively.

The findings are preliminary and should be interpreted cautiously because the sample was small, the study used an open-label design, and analyses were restricted to completers. The study also relied partly on self-reported cannabis use, used a binary abstinent/nonabstinent classification that could not capture gradual reduction, and did not collect cannabis potency or cannabinoid composition data at baseline.

In addition, all participants received structured weekly support and abstinence-contingent payments, so the extent to which symptom improvement reflected abstinence itself versus therapeutic engagement or behavioral reinforcement remains uncertain. The authors also stated that these results should not be generalized to people with PTSD who do not have comorbid cannabis use disorder.