Violent and sexual victimisation and incident anxiety, mood and substance use disorders in childhood and adolescence: a co-sibling study.

BACKGROUND: Studies on the association between victimisation in childhood and adolescence and psychiatric disorders increasingly acknowledge that these associations might be partly confounded by unmeasured familial factors. However, previous quasi-experimental evidence is largely based on retrospective self-reported data with potential response biases and small samples. METHODS: We measured psychiatric disorders and victimisation events from routinely collected administrative datasets on Finnish total birth cohorts 1996-2005. We identified all violent and sexual victimisation events using plaintiff information taken from registers containing data on crimes reported to the police between birth and the end of 2020. Incident anxiety, mood and substance use disorders were identified from registers containing records of inpatient and specialised outpatient psychiatric care. We compared all those exposed to victimisation to five population controls and their unexposed siblings, with the latter thereby adjusting for shared unobserved familial factors. We used stratified Cox regression models to estimate the associations between victimisation and the psychiatric disorders, with a follow-up from victimisation until the outcome, exit from the population or the end of 2020. RESULTS: Violent and sexual police-reported victimisation were both associated with an increased risk of psychiatric disorders, with adjusted hazard ratios ranging between 2.3 (95% Confidence Interval [CI]: 2.2, 2.4) for the association between violent victimisation and mood disorders and 3.9 (3.7, 4.1) for the association between sexual victimisation and anxiety disorders. In the sibling comparisons, the associations attenuated but remained clearly elevated, with the corresponding hazard ratios ranging between 1.9 (1.7, 2.1) and 2.6 (2.3, 2.9). CONCLUSIONS: The results are consistent with a causal interpretation of the association between police-reported victimisation and psychiatric disorders. Mental health-related support after victimisation is an important task as it may prevent the onset of psychiatric disorders. Prevention of victimisation might decrease the number of psychiatric disorders in the population.