Cognitive Processing Therapy for Veterans with Posttraumatic Stress Disorder: What is the Median Effective Dose?

Objective: Cognitive Processing Therapy (CPT) has been disseminated in the Veterans Health Administration (VHA) to treat posttraumatic stress disorder (PTSD). Identifying the median effective dose (MED) of CPT, the number of sessions at which the probability of experiencing clinically meaningful improvement (CMI) is 50%, can assist with treatment.

Method: From a cohort of Iraq and Afghanistan war veterans who received PTSD psychotherapy in VHA between 2001-2017, veterans who received CPT with available PTSD symptom outcomes (PTSD Checklist; PCL) were identified using natural language processing (n=26,189). Cox proportional hazards regression was used to examine how number of CPT sessions, together with covariates, influenced CMI (10-point PCL reduction). Kaplan-Meier curves were plotted to determine MED.

Results: At eight sessions, there was a 50% probability of experiencing CMI. The Cox proportional hazard regression indicated a greater likelihood of CMI in fewer sessions for veterans who received individual-only CPT versus any group CPT (HR:1.31, 95%CI:1.23-1.39). Kaplan-Meier curves indicated a 50% probability of experiencing CMI at seven sessions for veterans who received individual-only CPT versus ten sessions for veterans receiving any group CPT.

Limitations: PCL data was not available for all veterans who received CPT or at each potential assessment point. Not all veterans continued in CPT until CMI was observed.

Conclusions: The MED of CPT was eight sessions. Fewer sessions were needed to reach MED for veterans who received individual versus group CPT. These results may help those who treat, research, and are recovering from PTSD through accurately anchoring treatment expectations and providing a marker of initial treatment response.