1. In this retrospective study, Traumatic Brain Injury (TBI) was associated with a doubling in deaths by suicide, especially within the 6 months post-TBI.
2. The risk of suicide was higher in those with more severe TBI, numerous medical contacts, and longer hospital stays.
Traumatic Brain Injury (TBI) is known to lead to a higher rate of psychiatric symptoms, especially in the early recovery period. While suicide risk has been found to be elevated in some studies, these studies vary widely in the estimated risk and have rarely accounted for important co-variates, such as previous psychiatric history. In this large, retrospective cohort studying including the entire Danish population, the risk of suicide after TBI was found to be twice as high than in patients without TBI, especially within the first 6-months post-TBI. Further, the risk of suicide was greater for those with more severe TBI, numerous medical contacts, and longer hospital stays. As added specificity of the association, the risk of suicide after TBI was found to be elevated compared to those with non-skull fractures. Those with a psychiatric history before TBI were found to be at higher risk of suicide compared to those with TBI alone.
The rigorous study design, exploration of multiple co-variates and sensitivity analyses, and large cohort strongly suggests that TBI leads to higher suicide risk. Future studies determining which specific features of TBI increase suicide risk, such as subsequent disinhibition or depression, will be helpful in determining how TBI and suicide are mechanistically linked.
In-Depth [retrospective cohort]: Using a number of databases covering all those living in Denmark during the study period (1980-2014), 7,418,390 individuals over the age of 10 were tracked for diagnosis of TBI and death by suicide. Covariates in the basic statistical model included sex, age, and calendar year, and a full statistical model included these plus marital status, cohabitation status, socioeconomic status, other injuries, epilepsy, long-term physical disease using the Charlson co-morbidity index, pre-TBI psychiatric disorders, and pre-TBI self-harm behavior. TBI was associated with a 2.64 Incident Rate Ratio (IRR) for suicide in the basic model (CI95 2.55 to 2.74) and 1.90 in the full model (CI95 1.83 to 1.97). Those with severe TBI had a higher rate of suicide than those with mild TBI (IRR 1.32; CI95 1.21 to 1.44). Those with 1 medical contact for TBI had an IRR of 1.75 (CI95 1.68 to 1.83), 2 medical contacts had an IRR of 2.31 (CI95 2.13 to 2.51), and 3 or more medical contacts had an IRR of 2.59 (CI95 2.35 to 2.85). Increasing days in treatment for TBI was associated with higher suicide risk (p < 0.001). The risk of suicide within the first 6 months of TBI was higher than after (IRR 2.10; CI95 1.89 to 2.34). Those with psychological illness after their TBI had higher rates of suicide compared to TBI-only (IRR 4.90; CI95 4.55 to 5.29) and those with psychiatric illness before TBI had higher risks of suicide compared to those with TBI and no psychiatric illness (IRR 2.32; CI95 2.10 to 2.55). Those with TBI had a higher risk of suicide compared to those with non-CNS fractures (IRR 1.73; CI95 1.66 to 1.81).