Objective: To determine the incidence of psychiatric illness 3 years after mild traumatic brain injury (TBI) in children.
Design: Prospective cohort study with 3-year follow-up.
Setting: Emergency department, hospital, and outpatient clinics in a large health maintenance organization.
Participants: Children, 14 years old or less (n=490), who sustained a mild TBI in 1993. Three TBI unexposed subjects per TBI exposed patient were matched by sex, age, and enrollment at the time of injury (n=1470).
Interventions: Not applicable.
Main outcome measures: Computerized records were examined to identify psychiatric diagnoses, psychiatric medication prescription, and utilization of psychiatric services for the year before TBI and 3 years after. Adjusted relative risks for incidence of psychiatric illness were estimated for those with and without a premorbid psychiatric disorder.
Results: The cumulative incidence estimates for any psychiatric illness in the 3 years after mild TBI were 30% in children exposed to mild TBI and 20% in unexposed children (P=.0001). Cumulative incidence estimates were particularly high in both TBI exposed (55%) and unexposed children (63%) who had psychiatric illness in the year before the index TBI (psychiatric history). The exposed and unexposed children with psychiatric history did not have significantly different estimates of incidence during follow-up for any of the studied indicators of psychiatric illness. In those with no psychiatric history, 26% of exposed and 16% of unexposed children (P<.0001) had evidence of a psychiatric illness in the 3 years after mild TBI. For those with no psychiatric history, the adjusted relative risk estimate of any psychiatric illness in TBI exposed versus unexposed children, in the first year after TBI, was 2.03 (95% confidence interval [CI], 1.4-2.9). Children with mild TBI but no psychiatric history were at higher risk for hyperactivity (diagnosis of hyperkinetic syndrome of childhood or prescription of psychostimulants) in the first year after injury (incidence, 3%; first year relative risk, 7.59; 95% CI, 2.7-21.6).
Conclusions: In the 3 years after mild TBI, children with no evidence of prior-year psychiatric history were at significantly increased risk for psychiatric illness, particularly hyperactivity in the first year after injury. Prior-year psychiatric history conferred a significant independent risk for subsequent psychiatric illness. There was no evidence for an additional increase in risk in the 3-year follow-up that is attributable to mild TBI in children with prior psychiatric history.