Introduction Negative outcomes, including suicidal ideation/attempts, are a major public health concern, particularly among individuals who sustain a traumatic brain injury (TBI). TBI is associated with high rates of postinjury substance use, psychiatric disorders, post-traumatic stress disorder and sleep disturbances. This study examines the mediation effects of substance use, psychiatric disorder and sleep disorder on the associations between TBI and suicidal ideation/attempts.

Methods A matched case–control study using data from MarketScan databases for private health insurance and Medicaid from October 2015 to December 2018 estimated the association between TBI and suicidal ideation/attempts using a mediation approach. Individuals less than 65 years of age were included.

Results In the Medicaid sample, psychiatric disorders mediated 22.4% of the total effect between TBI and suicidal ideation/attempt, while substance use disorders other than opioid use disorder mediated 7.47%. In the private health insurance sample, psychiatric disorders mediated 3.97% of the total effect, opioid use disorders mediated 2.08% of the total effect and sleep disorder mediated 1.25% of the total effect.

Conclusions Mediators explained less than 30% of the relationship between TBI and suicidal ideation/attempt. Findings reinforce the importance of primary prevention of TBI and monitoring patients with a TBI for risk of suicide in the first 6–12 months following injury.