Traumatic brain injury (TBI) severity was tied to post-injury attention deficit hyperactivity disorder (ADHD) in children, a systematic review and meta-analysis showed. Odds for ADHD following severe TBI were higher for both ADHD onset within 1 year (OR 4.81, 95% CrI 1.66-11.03) and diagnosis more than 1 year later (OR 6.70, 95% CrI 2.02-16.82) compared to children with other injuries. The risks were also higher compared to non-injured controls (OR 2.62, 95% CrI 0.76-6.64, and OR 6.25, 95% CrI 2.06-15.06, respectively).