(PS4-96) The Relationship between Cannabis Use and PTSD Symptom Severity in Veterans and Active-Duty Service Members: Before and After Treatment in an Intensive Outpatient Program

Abstract Text: Veterans and active-duty service members (ADSM) face high rates of post-traumatic stress disorder (PTSD; Forbes et al., 2019). Veterans with a PTSD diagnosis are more likely to use cannabis and develop cannabis use disorder (CUD) than those without PTSD (Cougle et al., 201; Hill et al., 2021). However, the relationship between cannabis use and PTSD remains unclear. Prior research suggests that veterans with CUD have greater PTSD symptoms and poorer treatment outcomes compared to those without CUD (Livingston et al., 2022; Wilkinson et al., 2015). Other research suggests cannabis use has no impact on PTSD symptom change or that it may lead to greater PTSD symptom reduction than no cannabis use (Hale et al., 2020; Bonn-Miller et al., 2020). These mixed findings highlight the need for further research.

We compared PTSD symptom severity using the PTSD Checklist for DSM 5 (PCL-5; Weathers et al., 2013) among 2,597 Veterans and ADSM who did and did not endorse cannabis use in the two weeks prior to participating in an Intensive Outpatient Program (IOP) between January 2017 and January 2025. PTSD total and symptom cluster scores (intrusion, avoidance, negative alterations in mood and cognitions, and arousal) were compared before and after treatment. Participants were predominantly male (74.9%) and White (73.3%; further demographic data will be provided). They reported their cannabis use over the 14 days before treatment and completed the PCL-5 pre-and post-treatment. Participants were required to abstain from alcohol or substance use during the IOP.

Results showed that those who reported using cannabis at least once in the 14 days before treatment had significantly higher baseline PCL-5 total scores (M = 50.62, SD = 17.46) compared to those who did not use cannabis (M = 45.65, SD = 17.79), t(2596) = 5.96, p < 0.01, d = 0.28. Specifically, those who used cannabis had higher PCL-5 cluster B (p < 0.01, d = 0.18), C (p < 0.01, d = 0.19), D (p < 0.01, d = 0.37), and E scores (p < 0.01, d = 0.31) compared to those who did not use cannabis. Although post-treatment total PCL-5 scores did not differ significantly, those who used cannabis had significantly higher cluster B scores post-treatment (M = 9.91, SD = 5.33) compared to those who did not (M = 9.34, SD = 5.45),t(2241) = 2.05, p = 0.04, d = 0.11.

These findings suggest cannabis use may be associated with higher PTSD symptom severity at baseline and more persistent intrusive symptoms after treatment. Further clinical implications and limitations will be discussed.