• Overall PTSD symptoms: Not established. Six of seven controlled trials found no benefit over placebo. In the only trial of smoked cannabis, 80 veterans used high-THC, high-CBD, balanced, or placebo flower for 3 weeks: every group improved, including placebo, and no cannabis group did better (Bonn-Miller 2021). A 2026 Lancet Psychiatry review of 54 trials also found no benefit for PTSD.
• What veterans report outside trials: In a 2022 one-year observational study of 150 veterans by the same research group, those using medical cannabis reported larger drops in PTSD symptoms than those who did not (summary). Because veterans chose whether to use cannabis, this shows association, not proof. A 280-veteran trial of cannabis added to prolonged exposure therapy began in 2026 (NCT06222268).
• Trauma nightmares: Moderate. In a 2026 trial of 171 adults, bedtime dronabinol (prescription THC, 2.5 to 15 mg) reduced nightmare frequency and intensity more than placebo over 10 weeks. More than a third had no nightmares by the end. An earlier small trial of nabilone found the same direction of benefit.
• Overall PTSD severity and depression in that trial: No change.

Compared with standard treatment: Trauma-focused therapy remains first-line for PTSD. For nightmares, THC is a new option alongside prazosin and imagery rehearsal therapy.

Good to know: In the nightmare trial, 8% of patients on dronabinol had a serious adverse event, versus none on placebo. People with PTSD are at higher risk of problem cannabis use. Tell your mental health provider what you use.

For veterans: Veterans will not lose VA benefits for using medical cannabis in a state where it is legal, and can discuss it with VA clinicians. As of October 2026, VA clinicians still cannot recommend cannabis or complete state certification forms, and the VA/DoD PTSD guideline recommends against cannabis as a PTSD treatment. In May 2026 the House voted to let VA doctors recommend medical cannabis; that change has not taken effect. Veterans in New York can be certified by any registered non-VA practitioner.

What to ask for: For nightmares, low-dose THC taken by mouth at bedtime, ideally prescription dronabinol, which is what the trial used. Smoked high-THC flower did not help overall PTSD symptoms.