Socioeconomic sequelae of drug abuse in a Swedish national cohort

Background: Drug abuse is frequently associated with negative sequelae such as reduced socioeconomic functioning. The extent to which these associations are attributable to a causal role of the disorder versus confounding factors that increase risk for both drug abuse and negative socioeconomic outcomes is unclear. Methods: Drug abuse cases were identified using Swedish national medical, pharmacy, and criminal registers. Applying Cox proportional hazard models, we tested the association between drug abuse and four outcomes: early retirement, social assistance, unemployment, and income at age 50. We used co-relative models to determine whether familial confounding factors accounted for observed associations. Results: In models adjusted for birth year, education, and early onset externalizing behavior, drug abuse was strongly associated with early retirement (hazard ratios [HR] = 5.13–6.28), social assistance (HR = 6.74–7.89), and income at age 50 (beta = −0.19 to −0.12); it was more modestly associated with unemployment (HR = 1.05–1.20). For social assistance and income (both sexes), and early retirement (women only), a model in which the association was partly attributable to familial factors fit the data well; residual associations support a partially causal role of drug abuse. For unemployment and early retirement among men, there was little evidence of familial confounding. Conclusions: The negative socioeconomic sequelae of drug abuse are likely due in part to familial confounding factors in conjunction with a causal relationship and/or unmeasured non-familial confounders. Relative contributions from distinct mechanisms differed across socioeconomic outcomes, which could have implications for understanding the potential impact of prevention and intervention efforts.