Parental traumatic brain injuries and their association with major depressive disorder in offspring: A study based on national registers in Finland

BACKGROUND: Traumatic brain injuries (TBIs) can cause long-term brain dysfunction. Clinical studies suggest that parental TBI increases the risk of depressive symptoms in offspring. We aimed to investigate: 1) the association between parental TBI of different severities and later diagnosed offspring major depressive disorder (MDD) and 2) the association between the first parental TBI after offspring birth and subsequent offspring MDD, depending on child's age at injury. METHODS: This nested case-control study identified 37,682 cases aged ≤25 years, 148795 matched controls, and their parents from Finnish national registers. Associations were calculated applying conditional logistic regression, comparable to Cox regression in this study design. Hazard ratios (HR) were estimated with 95% confidence intervals and two-sided significance limits, p < 0.05. Associations were adjusted for parental psychopathology and maternal socio-economic status. RESULT: After adjustments, maternal and paternal TBIs of all severities were associated with offspring MDD. Concussions {aHR(maternal) 1.26 (95% CI 1.18-1-35); aHR(paternal) 1.14 (95% CI 1.07-1.21)}. Severe intracranial head injuries {aHR(maternal) 1.39 (95% CI 1.18-1.65); aHR(paternal) 1.30 (95% CI 1.18-1.44)}. Any first-time parental TBI occurring after offspring birth was associated with MDD in offspring, aged 1-18 years for mothers and aged 1-12 years for fathers. The association was strongest for offspring aged 0-6 years when maternal TBI happened {aHR 1.47 (95% CI 1.22-1.78)}. LIMITATIONS: Diagnoses were register-based without direct ascertainment. CONCLUSIONS: Parental TBIs of all severities were associated with offspring MDD. These families may need supportive services, with special attention warranted for maternal TBI when children are very young.