Predictors of attendance and dropout in three randomized controlled trials of PTSD treatment for active duty service members.

Dropout from first-line posttraumatic stress disorder (PTSD) treatments is a significant problem. We reported rates and predictors of attendance and dropout in three clinical trials of evidence-based PTSD treatments in military service members (N = 557). Service members attended 81.0% of treatment sessions and 30.7% dropped out. Individually delivered treatment was associated with greater attendance rates (β = 0.23, p < .001) than group therapy; trauma-focused treatments were associated with higher dropout (β = 0.19, p < .001) than Present-Centered Therapy. Age was a significant predictor of session attendance (β = 0.17, p < .001) and drop out (β = -0.23, p < .001). History of traumatic brain injury (TBI) predicted lower attendance rates (β = -0.26, p < .001) and greater dropout (β = 0.19, p < .001). Regardless of treatment type or format, patients who did not drop out were more likely to experience clinically significant gains (d = 0.49, p < .001). Results demonstrate that dropout from PTSD treatments in these trials was significantly associated with treatment outcome and suggest that strategies are needed to mitigate dropout, particularly in group and trauma-focused therapies, and among younger service members and those with TBI.