Unexpected adverse childhood experiences and subsequent drug use disorder: a Swedish population study (1995-2011).

AIMS: Exposure to extraordinary traumatic experience is one acknowledged risk factor for drug use. We aim to analyse the influence of potentially life-changing childhood stressors, experienced second-hand, on later drug use disorder in a national population of Swedish adolescent and young adults (aged 15-26 years).
DESIGN: We performed Cox proportional hazard regression analyses, complemented with co-relative pair comparisons.
SETTING: Sweden. PARTICIPANTS: All individuals in the Swedish population born 1984-95, who were registered in Sweden at the end of the calendar year that they turned 14 years of age. Our follow-up time (mean 6.2 years; range 11 years) started at the year they turned 15 and continued to December 2011 (n = 1,409,218). MEASUREMENTS: Our outcome variable was drug use disorder, identified from medical, legal and pharmacy registry records. Childhood stressors, as per DSM-IV stressor criteria, include death of an immediate family member and second-hand experience of diagnoses of malignant cancer, serious accidental injury and victim of assault. Other covariates include parental divorce, familial psychological wellbeing and familial drug and alcohol use disorders.
FINDINGS: After adjustment for all considered confounders, individuals exposed to childhood stressors 'parental death' or 'parental assault' had more than twice the risk of drug use disorder than those who were not [hazard ratio (HR) = 2.63 (2.23-3.09) and 2.39 (2.06-2.79), respectively].
CONCLUSIONS: Children aged under 15 years who experience second-hand an extraordinary traumatic event (such as a parent or sibling being assaulted, diagnosed with cancer or dying) appear to have approximately twice the risk of developing a drug use disorder than those who do not.