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Mutual relationships between head injury and conduct problems in children aged 9 months to 14 years in the UK Millennium Cohort Study

Background: Research suggests a link between acquired head injury and signs of conduct disorder, with a majority of findings based on retrospective reports and comparison samples. The relationship between head injuries and conduct problems and how they may influence one another during development is currently unclear. This study aimed to investigate direct and indirect associations between head injury and conduct problems through to early adolescence. Methods: Data from the UK Millennium Cohort Study was used to investigate the relationship between conduct problems as assessed by the Strengths and Difficulties Questionnaire and parent reported head injury over time, at ages 9 months, 3, 5, 7, 11 and 14 years, using a cross-lagged path analysis. This is data from 18,552 children, participating in a UK cohort study that is representative of the UK population. We included 7,041 (3,308 male) children, who had full information about head injuries and conduct problems at age 14. Results: We found a mutual association between childhood head injuries and conduct problems but with distinct timings: Head injury between 5-7 years predicted greater chance of conduct problems at age 11 and 14 years, while greater conduct problems at 5 years predicted a significantly greater chance of a head injury at age 7-11 years. Conclusions: These findings have important implications for the timing of preventive and ameliorative interventions. Prior to school entry, interventions aiming to reduce conduct problems would appear most effective at reducing likelihood of head injuries in future years. However, equivalent interventions targeting head injuries would be better timed either as children are entering formal primary education, or soon after they have entered.