MPO and post-traumatic stress disorder: Additionally, we observed that, in PTSD participants, GSH in the DLPFC (but not in the ACC) is elevated in cannabis users and in individuals with a history of mTBI (albeit a small n = 10 sample size); that MPO was associated with cannabis use and comorbid MDD and that TIMP-1 was elevated among PTSD participants who endorsed SSRI use.