Within Day Variation in Posttraumatic Stress Disorder Symptom Clusters

Objective: Posttraumatic stress disorder (PTSD) has four symptom clusters: intrusion, avoidance, negative cognitions/mood, and hyperarousal. Little is known about the extent to which the intensity of the symptom clusters vary from moment-to-moment. Using an ecological momentary assessment methodology, this study examined within day variation in the four PTSD symptom clusters. Methods: Participants with PTSD (N = 78) completed self-report assessments of 18 posttraumatic stress symptoms (PTSS) four times daily for 15 days. Linear mixed models and linear spline models examined how PTSS and each of the four PTSD symptom clusters varied across six daily time-blocks (0700, 1000, 1300, 1600, 1900, 2200). Results: PTSS and each symptom cluster differed across the six time-blocks: PTSS, F(5, 345) = 10.06, p <.001; intrusion: 3.02, p <.05; avoidance: 11.31, p <.001; negative cognitions/mood: 7.42, p <.001; and hyperarousal: 9.34, p <.001. All symptom clusters were lowest at the first time-block with an overall increasing pattern across the six time-blocks. Knot analyses indicated maximum symptoms of intrusion at 1000, while maximum symptoms of avoidance, negative cognitions/mood, and hyperarousal occurred at 1300. Conclusions: All four PTSD symptom clusters vary within a day, are lowest in the morning and peak at different times. Further study of the causes of this within day variation, including the neurobiological, psychological, behavioral, and lifestyle factors is important for understanding the mechanisms of and interventions for PTSD.