Correspondence Between Retrospective and Momentary Self-Reported Posttraumatic Stress Disorder Symptoms: Evidence for Peak and End Effects in Veterans.

Validated retrospective self-report symptom rating scales are recommended for posttraumatic stress disorder (PTSD) screening and treatment. However, such reports may be affected by a respondent's most intense ("peak") or most recent ("end") symptoms. The present study evaluated the correspondence between PTSD symptoms assessed using a standard past-month retrospective rating scale and recorded by ecological momentary assessment (EMA) over the same period and tested hypotheses that retrospective scores would be predicted by peak and end-period momentary symptoms. Male U.S. veterans (N = 35) who served post-9/11 completed the PTSD Symptom Checklist for DSM-5 (PCL-5) at baseline and 1 month later. For 28 days during the intervening period, they received quasi-randomly timed text prompts to complete a modified version of the PCL-5 at that moment. Using multiple regression modeling, controlling for the number of completed EMAs and time (days) since the last EMA, we assessed the predictability of follow-up retrospective PCL-5 scores by (a) the mean of all momentary scores and (b) peak and last-day momentary scores. Retrospective PCL-5 scores were closest to peak scores, d = -0.31, and substantially higher than overall mean, d = 0.99, and last-day momentary scores, d = 0.94. In the regression model, peak symptom experiences and last-day momentary symptoms uniquely predicted follow-up PCL-5 scores over and above significant prediction by overall mean momentary symptom scores. In sum, participants' self-reported past-month PTSD symptom severity did not simply reflect an average over time. Additional questioning is needed to understand peak and recent symptom periods reflected in these estimates.