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.
Telling people they are consuming a cannabis-infused edible can produce feelings of intoxication even when the product contains no active drug. In a study of 20 participants who were given a placebo lollipop but told it contained a high dose of THC, measures of cannabis intoxication and negative mood showed significant changes over 60 minutes, while positive mood and a general intoxication measure did not. This provides preliminary evidence that the placebo effect extends to edible cannabis products, which have a delayed onset of effect.