People with traumatic brain injury (TBI) have increased rates of subsequent depression; however, these rates have not been compared with depression rates in the background population. A national register-based cohort study compared rates of depression in people who experienced TBI between 1977 to 2015 in Denmark (n=494.216) versus a sex- and age-matched reference population (n=499,505). During the follow-up period (14.5 ± 11.3 years), 5.6% of individuals with TBI and 3.0% of individuals in the reference population were diagnosed with depression, such that TBI was associated with 16.6 (95% confidence interval [CI]: 16.1-17.2) more cases of depression per 10,000 person years. First-time TBI was associated with a higher risk of depression in both men (hazard ratio [HR]: 2.10, 95% CI: 2.04-2.17) and women (HR: 1.90, 95% CI: 1.85-1.96). A significant dose-dependent association between number of TBIs and depression diagnosis was detected in both men and women (Figure 1). Finally, the study showed that the risk for depression was highest during the first 6 months after the TBI in both men (HR: 5.56, 95% CI: 5.46-6.55) and women (HR: 4.55, 95% CI: 3.93-5.26) and decreased gradually the following year but remained significantly elevated from one year after the TBI until the end of follow-up. In line with previous research, the current study found that TBI was associated with a 66-73% higher risk of depression and this risk was highest during the first six months (4.55- to 5.46-fold higher risk) post-TBI but persisted more than one year after. This study also adds to the literature by showing a dose-dependent association between TBI and depression. Clinicians should be vigilant about the risk of depression following TBI, particularly during the first months after the TBI and in cases where there is a history of previous TBI.
The dose-dependent association between the number of traumatic brain injuries and depression diagnosis in men and women. Hazard risks (95% confidence intervals) are presented for each number of traumatic brain injuries. Depression diagnosis includes cases of recurrent and new-onset depression. This association held in sensitivity analyses that were restricted to new-onset depression diagnoses. No individuals had ongoing depression up to one year before their first traumatic brain injury. HR: hazard ratio; TBI: traumatic brain injury.
Eliasen MH et al. Acta Psychiatr Scand; Epub ahead of print. Abstract