A randomized placebo-controlled trial tested three concentrations of smoked cannabis (high THC, high CBD, THC+CBD) against placebo in military veterans with PTSD. Over three weeks, all groups including placebo showed significant improvements in PTSD symptom severity, but none of the active cannabis concentrations outperformed placebo statistically. The treatments were generally well tolerated. This preliminary trial did not find evidence that smoked cannabis is more effective than placebo for PTSD symptoms in the short term, highlighting the need for further well-powered studies.
Classical psychedelics such as psilocybin, ayahuasca, and LSD produce significant psychological effects lasting at least 24 hours after administration, according to a systematic review and meta-analysis of 34 experimental studies involving 549 participants. Large effects were observed for reducing targeted symptoms in psychiatric samples, improving negative and positive affect, social outcomes, and existential or spiritual well-being, with between-group effect sizes ranging from Hedges' g = 0.84 to 1.08. Effects may be larger in clinical samples. Evidence for changes in personality traits or mindfulness was weak. No post-acute adverse effects were found, but high risk of bias, heterogeneity, and possible publication bias underscore the need for larger, placebo-controlled trials.