In this trial, the investigators will recruit veterans with post-traumatic stress disorder (PTSD) who report using cannabis. Veterans will be assigned (via participant self-selection) into either a naturalistic group that will be followed as the participants continue to use cannabis as they normally do (observation only), or into a "THC (tetrahydrocannabinol) reduction group" in which veterans are asked to switch from their typical cannabis product to using a lower THC/higher Cannabidiol (CBD) product; adherence to this switch will be incentivized using a behavioral intervention called contingency management (CM).
