Risk of substance use disorders in the adult children of parents with severe alcohol use disorder: a nationwide cohort study

Offspring of parents with alcohol use disorder (AUD) have elevated risk of substance use. However, few studies have comprehensively assessed risks associated with different substances. This study investigated the risk of substance use disorders (SUDs) in adult children with severe parental AUD over four decades, contributing information on the risk of each disorder, the roles of important risk factors, and the general versus substance-specific nature of SUD risk. Swedish national register data were used to follow children with and without ≥ 1 parent with an inpatient diagnosis of AUD from 1973 to 2018 to investigate risk of alcohol, opioid, cannabinoid, sedative/hypnotic, cocaine, other stimulant, hallucinogen, volatile solvent, and multiple drug use disorder. The composite outcomes any SUD, 1 SUD, and ≥ 2 SUDs including and excluding AUD were also investigated. Severe parental AUD and outcomes were defined with hospital inpatient diagnoses (ICD codes). Hazard ratios (HRs) were calculated with Cox regression. Model 1: unadjusted. Model 2: adjusted for child’s sex, parental education, and parental mortality. Model 3: Model 2 plus parental SUD. Model 4: Model 3 plus parental psychiatric disorder. Risks of all outcomes were higher in those with (n = 99,723) than without (n = 2,321,756) severe parental AUD. For SUD diagnoses, the highest unadjusted risks were for other stimulant (HR 5.33, 95% CI 5.03–5.64), volatile solvent (HR 4.95, 95% CI 3.98–6.15), and opioid (HR 4.62, 95% CI 4.37–4.87) use disorders. After full adjustment, risks declined, and HRs of the different diagnoses converged to approximately twice as high in the adult children of parents with AUD. Risks of any SUD and of ≥ 2 SUDs were more elevated (95% CIs did not overlap) when AUD was included than when AUD was excluded. Risk of ≥ 2 SUDs was higher than risk of 1 SUD, but only when AUD was included. Severe parental AUD was associated with elevated risk for all SUDs. After full adjustment, SUD risks declined and converged but remained doubled. Sociodemographic factors, parental SUD, and parental psychiatric disorder explained much of the excess risk. Drug combinations that included alcohol elevated the risk of ≥ 2 SUDs and any SUD.