This randomized, double-blind, placebo-controlled, between-subjects study was published in June 2020 in the journal Psychopharmacology. It examined the effects of low-dose THC on human brain responses to threats.
The study tested three groups of adults: 1) Non-trauma exposed healthy controls, 2) trauma-exposed adults without PTSD, and 3) trauma-exposed adults with PTSD.
The study showed that LOW DOSE THC was beneficial for reducing anxiety and fear among those adults with PTSD. This is consistent with the biphasic nature of THC, in that high doses can have the OPPOSITE effects of small doses.
"These preliminary data suggest that THC modulates threat-related processing in trauma-exposed individuals with PTSD, which may prove advantageous as a pharmacological approach to treating stress- and trauma-related psychopathology."
The abstract is available here from the National Library of Medicine.