Association Between Impulsivity, Self-Harm, Suicidal Ideation, and Suicide Attempts in Patients with Traumatic Brain Injury

Traumatic brain injury (TBI) affects over 48 million people worldwide each year. Suicide is common in TBI, and there are several known contributing factors, including severe TBI, depression, alcohol use, and male sex. Impulsivity, or the tendency to act quickly with little thought, may be an early predictor of suicidality following TBI. The purpose of this study was to evaluate the risk of suicidality in patients with a prior history of impulsivity following a TBI. Using de-identified electronic health records from the TriNetX U.S. Collaborative Network with Natural Language Processing, three cohorts were generated: the impulsivity TBI cohort (I+TBI+) included subjects with a diagnosis of impulsivity before a diagnosis of TBI; the no impulsivity TBI cohort (I-TBI+) included patients with TBI but no impulsivity; the impulsivity no TBI cohort (I+TBI-) included patients with impulsivity but TBI. Two analyses were conducted, including analysis 1 (impulsivity TBI vs. no impulsivity TBI) and analysis 2 (impulsivity TBI vs. impulsivity no TBI). Patients were 1:1 matched by age, sex, race, ethnicity, psychiatric diagnoses, and antidepressant use. Outcomes included a diagnosis of self-harm, suicidal ideation, or a suicide attempt within 1 year after the index event. The all-time incidence of each outcome was assessed across different age categories. The chi-square test (categorical variables) and <i>t</i>-test (numerical variables) were used to assess for differences between groups. A total of 1,292,776 patients with TBI were identified in the study. After 1:1 matching, there were 20,694 patients (mean [standard deviation, SD] age, 48.1 [21.8]; 8,424 females [40.7%]) with impulsivity and TBI (I+TBI+), 1,272,082 patients (mean [SD] age, 46.0 [23.1]; 562,705 females [44.2%]) with TBI alone (I-TBI+), and 90,669 patients (mean [SD] age, 43.7 [22.6]; 45,188 females [49.8%]) with impulsivity alone (I+TBI-). Within the first year after a TBI, patients with impulsivity were more likely to exhibit self-harm (<i>p</i> < 0.001), suicidal ideation (<i>p</i> < 0.001), or a suicide attempt (<i>p</i> < 0.001). Compared with patients with TBI without impulsivity, those with impulsivity had a 4-fold increase in the incidence of self-harm (2.81% vs. 0.63%), an 8-fold increase in suicidal ideation (52.42% vs. 6.41%), and a 21-fold increase in suicide attempts (32.02% vs. 1.50%). This study suggests that impulsivity diagnosed before a TBI may increase the risk of post-traumatic suicidality, with a 4-fold increased risk of self-harm, an 8-fold increased risk of suicidal ideation and a 21-fold increased risk of suicide attempts. This characterizes a group of at-risk individuals who may benefit from early psychiatric support and targeted interventions following a TBI.