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Medicinal cannabis for treating PTSD and comorbid depression: Real World Evidence from Project T21

Someone holding a cannabis plant in their hand


Michael Lynskey, Alkyoni Athanasiou-Fragkouli, Hannah Thurgur, Anne Schlag and David Nutt


March 12, 2024


Cannabis-based medicinal products (CBMPs) are increasingly being used to treat post-traumatic stress disorder (PTSD), despite limited evidence of their efficacy. PTSD is often comorbid with major depression, and little is known about whether comorbid depression alters the effectiveness of CBMPs.



To document the prevalence of depression among individuals seeking CBMPs to treat PTSD and to examine whether the effectiveness of CBMPs varies by depression status.



Data were available for 238 PTSD patients (5.9% of the sample) and three-month follow-up data were available for 116 patients. Self-reported PTSD symptoms were assessed at treatment entry and at three-month follow-up using the PTSD CheckList – Civilian Version (PCL-C). The probable presence of comorbid depression at treatment entry was assessed using the Patient Health Questionnaire-9 (PHQ-9). Additional data included sociodemographic characteristics and self-reported quality of life.



77% met screening criteria for depression, which was associated with higher levels of PTSD symptomatology (67.8 vs 48.4, F(1,236) = 118.5, p<.001) and poorer general health, quality of life and sleep. PTSD symptomatology reduced substantially three months after commencing treatment (58.0 vs 47.0, F(1,112)=14.5, p<.001), with a significant interaction (F(1,112)=6.2, p<.05) indicating greater improvement in those with depression (mean difference = 15.3) than in those without (mean difference = 7).



Depression is common among individuals seeking CBMPs to treat PTSD and is associated with greater symptom severity and poorer quality of life. Effectiveness of CBMPs for treating PTSD does not appear to be impaired in people with comorbid depression.

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