The association between childhood mild traumatic brain injury and adolescent criminal behavior nearly disappeared when accounting for family-level confounding factors in over 340,000 participants, according to a recent study.

In the cohort study, published in JAMA Pediatrics, investigators examined the association between childhood mild traumatic brain injury (mTBI) prior to age 10 and subsequent criminal charges or convictions in adolescence. The analysis included 343,027 individuals born in Denmark from 1995 to 2000, with data linking mTBI diagnoses before age 10 to criminal charges and convictions between ages 15 and 20. The exposure group consisted of those diagnosed with mTBI, whereas the comparison group included participants without mTBI or other head injuries.

The exposure group consisted of 13,514 participants diagnosed with mTBI prior to 10 years of age and the comparison group included 329,513 participants without a diagnosis of mTBI or any other intracranial or extracranial injuries. The study population was 49% female (n = 166,455) and 51% male (n = 176,572). In terms of citizenship, 95% of the participants had at least one parent with Danish citizenship, and 23% of mothers had completed a college education.

Initial results demonstrated a significant association between mTBI and criminal justice involvement odds ratio (OR) for criminal charges of 1.26 and for convictions of 1.24. The rate of criminal charges was 8.4% among those in the mTBI group compared with 6.3% in the group without mTBI. For criminal convictions, 6.6% of participants in the mTBI group had convictions vs 5.0% in the non-mTBI group. This indicated a 33% higher risk for charges and a 32% higher risk for convictions in the mTBI group before adjusting for family-level confounders.

However, the associations diminished and became statistically insignificant after adjusting for family-level confounding factors through sibling and twin fixed-effect models. The investigators suggested that the observed link between mTBI and criminal behavior may not be causal and could be attributed to shared familial risk factors. When using sibling and twin fixed-effect models to adjust for family-level confounders, the associations between childhood mTBI and criminal charges (OR = 0.97, 95% confidence interval [CI] = 0.85–1.10) and convictions (OR = 0.95, 95% CI = 0.82–1.09) were no longer statistically significant. Twin fixed-effect models showed similar point estimates, but with larger standard errors as a result of the smaller sample size (OR for charges = 0.94, 95% CI = 0.58–1.53; OR for convictions = 0.84, 95% CI = 0.51–1.41).

The investigators concluded that mTBI in childhood does not independently cause criminal behavior in adolescence. Although mTBI is associated with behavioral problems and mental health disorders, interventions aimed solely at reducing mTBI are unlikely to directly impact adolescent criminality. The study controlled for family-level influences when evaluating the relationship between mTBI and criminal outcomes.

This research utilized Denmark's comprehensive population-based data and indicated that associations between childhood mTBI and criminal justice involvement became statistically insignificant when controlling for family-level confounders. 

Full disclosures can be found in the published study.