Currently submitted to: JMIR mHealth and uHealth
Date Submitted: Aug 10, 2026
Open Peer Review Period: Aug 12, 2026 - Oct 7, 2026
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Examining the Relationship between Changes in Daytime Activity Structure and PTSD Symptoms during a 4-Week Morning Light Treatment: A Treatment Study
ABSTRACT
Background:
Posttraumatic stress disorder (PTSD) is associated with circadian rhythm disruption. Morning light treatment (MLT) decreases PTSD symptoms, yet there has been limited research on the mechanisms underpinning the effectiveness of this treatment in reducing PTSD symptoms. Modifying daytime activity patterns may serve as a mechanism for regulating circadian rhythms during MLT for traumatic stress.
Objective:
This study aims to understand the lagged relationships between changes in activity, sleep, and PTSD symptoms during a four-week morning light treatment.
Methods:
Participants (N = 46; mAge = 33.7, sdAge = 10.6; 73.9% female) were randomized to receive 15, 30, or 60 minutes of MLT each morning after waking for 4 weeks. During the intervention, participants continuously wore actigraphy watches and completed weekly assessments of their PTSD symptoms (PTSD Checklist for DSM-5 [PCL-5]). Recurrence quantification analysis (RQA) was used to calculate the laminarity (LAM; stability of activity patterns), determinism (DET; temporal predictability in activity patterns), and entropy (ENTR; complexity of activity patterns) of daytime activity patterns. Traditional sleep actigraphy metrics (total sleep time, sleep efficiency, and sleep midpoint) were calculated as well. Linear mixed effects models were then used to assess whether lagged week-to-week changes in sleep and daytime activity patterns (T-2 to T-1) predicted subsequent changes in PTSD symptoms at the following time point (T-1 to T) as well as the reverse lagged relationships. A random intercept was included to account for repeated measures nested within individuals.
Results:
Increases in the stability (p = .032) and temporal predictability (p = .030) of daytime activity patterns were significantly associated with subsequent reductions in PTSD symptoms. Changes in activity complexity, total sleep time, sleep midpoint, and sleep efficiency were not associated with subsequent PTSD symptom change (ps > .05). When the reverse relationships were examined, changes in PTSD symptoms did not predict later changes in daytime activity pattern stability, predictability, or complexity. Additionally, PTSD symptom changes during the intervention were not significantly associated with changes in total sleep time, sleep efficiency, and sleep midpoint.
Conclusions:
Increases in daytime activity stability and predictability were associated with subsequent improvements in PTSD symptom severity during a morning light intervention. Compared to traditional actigraphy variables, some metrics captured through recurrence quantification analysis demonstrated a stronger effect in predicting subsequent PTSD symptom changes during the intervention. Modifying activity patterns may contribute to PTSD symptom change through circadian rhythm interventions.
Citation
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