Measuring PTSD course among substance use disorder patients: A pilot study of the interrater reliability and validity of the Longitudinal Interval Follow-Up Evaluation (LIFE)

Posttraumatic stress disorder (PTSD) and substance use disorders (SUDs) often co-occur. Methods that can map symptom occurrences over time may shed light on the potential etiological and maintaining factors of such complex symptom presentations. The Longitudinal Follow-Up Evaluation (LIFE) is an assessment method that has been used to characterize the weekly course of psychiatric disorder. This pilot study examined the interrater reliability and concurrent validity of LIFE to assess PTSD and substance dependence symptom course over a period of 26 weeks among SUD outpatients (N = 35). Participants with trauma histories completed interviews, including the LIFE for the prior 6 months, and questionnaires. All interviews were scored by a second rater. Results indicated good interrater reliability for the weekly psychiatric status ratings (PSRs). Associations between PTSD and SUD PSRs with alternative measures of PTSD, substance use and abuse, and functional status supported the validity of the PSRs. These data suggest that the LIFE is a reliable and valid method to measure weekly symptoms of PTSD. This method may prove helpful in mapping the course of PTSD-SUD and, as such, allowing more rigorous tests of process-related models of PTSD and SUD such as self-medication.