Socioeconomic sequelae of drug abuse in a Swedish national cohort.

Abstract

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. 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. 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. 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.