Cannabis Vapor Weakens Traumatic Fear Memories Long-Term, with Sex-Specific Effects

Acute cannabis vapor before conditioning had no immediate effect on fear acquisition but impaired fear recall in females 24 hours later and prevented spontaneous recovery of fear in both sexes at two weeks. Acute exposure before extinction impaired extinction in females but enhanced it in males. Chronic THC exposure initially potentiated fear responses (mainly in females) but produced no long-term differences.

Male and female Sprague Dawley rats were exposed to THC-dominant cannabis extract or vehicle vapor, then assessed in Pavlovian auditory fear conditioning. Both passive (freezing) and active (darting) fear behaviors were measured during conditioning, extinction, retrieval, and 2-week spontaneous recovery.

PTSD treatments often fail because extinguished fear memories return over time (spontaneous recovery). Cannabis's ability to prevent this return — especially the long-term destabilization effect — could inform new approaches to trauma therapy.

The most striking finding — that a single cannabis exposure before a traumatic event prevents the fear memory from returning weeks later — suggests cannabis may destabilize fear memories in ways that could fundamentally change PTSD treatment timing and strategy.

Rodent fear conditioning is a simplified model of human PTSD. Cannabis vapor composition may differ from human products. Sex differences complicate clinical translation. Acute exposure paradigm doesn't match typical human use patterns.