Association between paediatric mild traumatic brain injury, subsequent psychiatric problems and mental health service use: a longitudinal cohort study

<h3>Background</h3> Evidence that mild traumatic brain injury (mTBI) causes psychiatric problems in children has been mixed. Investigating this issue has been difficult due to the lack of representative data on child mTBI that includes adequate measures of subsequent mental health symptoms and service use in young people. <h3>Methods</h3> We used data from the ABCD longitudinal cohort study to examine the association between mTBI and psychiatric diagnoses, symptoms, and psychiatric service use in over 11,000 children aged 9–10 at baseline, and subsequently, any new cases of mTBI since baseline and psychiatric outcomes and service use at two-year follow-up. To strengthen causal inference, we included a comparison group of participants with orthopaedic injury (OI) but without mTBI. Mixed-effects models were used and adjusted for demographic and social covariates, with missing data imputed using random forest multiple imputation. New cases of mTBI/OI in the 24 months following baseline were also propensity-score matched to those with no injury to control for baseline mental health. <h3>Results</h3> Both lifetime mTBI at baseline, and new occurrence of mTBI at two-year follow-up, were reliably associated with an increased risk of DSM-5 anxiety and behavioural disorders, mental health symptom scores measured psychometrically, and increased psychiatric service use. These associations remained after adjustment for a range of potential confounders. These associations were not present, or occasionally only minimally present, in the OI comparison group. However, propensity-score matching which controlled for baseline mental health resulted in no associations between mTBI and psychiatric symptoms, diagnoses and service use, with the exception of parent-reported anxiety and conduct symptom scores. <h3>Conclusion</h3> This work provides evidence that the association between childhood mTBI and subsequent psychiatric problems and service use may be largely explained by pre-existing mental health problems and emphasises the importance of longitudinal research in this area.