Predictors of Depressive Symptoms in Post-Concussion Syndrome: Role of Pre- and Post-Injury Substance and Medication Use

BackgroundDepression is frequently encountered in patients suffering from post-concussive syndrome (PCS) after mild traumatic brain injury (mTBI). Clinical strategies for predicting and managing such depression remain underdeveloped.ObjectiveTo determine whether pre- and post-injury alcohol, tobacco, marijuana, and antidepressant medication use are associated with risk of depression in PCS.MethodsWe conducted a retrospective chart review of 297 patients diagnosed with PCS at a Honolulu neurology clinic between January 2020 and January 2023, analyzing substance and antidepressant use patterns before and after PCS diagnosis and their relationship to post-injury depression risk using PHQ-2 scores.ResultsOf screened patients, 31% were identified as at risk for depression after concussion. Pre-injury tobacco use and marijuana use (both before and after concussion) were significantly associated with greater depression risk. Notably, prior antidepressant use emerged as a strong predictor of depression following concussion, particularly for those who discontinued antidepressants after injury. Patients co-using marijuana and antidepressants had the highest risk.ConclusionsTobacco, marijuana, and exposure to antidepressants prior to concussion, especially discontinuation of these agents, are key risk factors for depression in PCS. These findings emphasize the importance of proactively screening patients with post-concussion syndrome for psychiatric symptoms. Regular assessment of substance use and close monitoring of antidepressant adherence should be integrated into neurorehabilitation care. A coordinated, multidisciplinary approach involving neurology, physiatry, psychiatry, and addiction specialists is essential to identify and address these risk factors early, improving patient outcomes through timely intervention. Future studies should clarify mechanisms and optimal intervention timing.