Baseline Depressive Symptoms Do Not Moderate the Association Between Baseline Symptom Severity and Time to Recovery in Individuals with Grade I-II Whiplash-Associated Disorders: A Secondary Analysis of a Randomized Controlled Trial.

Objective: This study investigated the moderating role of baseline depressive symptoms on the association between baseline pain severity and time to recovery in individuals with acute grade I-II whiplash-associated disorders.

Design: This is a secondary analysis of a randomized controlled trial investigating the effectiveness of a government-regulated rehabilitation guideline for the management of grade I-II whiplash-associated disorders. Participants who completed baseline questionnaires for neck pain intensity and depressive symptoms and follow-up questionnaire on self-reported recovery were included in the analysis. Cox proportional hazards models were built, and hazard rate ratios were reported to describe the association between baseline neck pain intensity and time to self-reported recovery and to assess the effect modification of baseline depressive symptoms.

Results: Three hundred three participants provided data for this study. Despite baseline level of depressive symptoms and neck pain intensity being independently associated with delayed recovery, the association between baseline neck pain intensity and time to recovery was not stronger for individuals with significant postcollision depressive symptoms (hazard rate ratio = 0.91; 95% confidence interval = 0.79-1.04) than for those without depressive symptoms (hazard rate ratio = 0.92; 95% confidence interval = 0.83-1.02).

Conclusions: Baseline depressive symptoms are not an effect modifier of the association between baseline neck pain intensity and time to self-reported recovery in acute whiplash-associated disorders.