Aim To assess the prevalence of substance use and other psychiatric disorders in first-degree relatives of males with opioid dependence compared to normal controls.
Design Observational, case–control study using family history method.
Setting A drug addiction treatment centre in northern India.
Participants First-degree relatives of 100 male probands with opioid dependence and no comorbidity (n = 493) and those of 50 matched probands from normal population (n = 254).
Measurement Family interview of probands and family members, using the Family Interview for Genetic Studies. The main outcome measure was relative risk (expressed as odds ratio after controlling for confounding variables using logistic regression) of familial aggregation of psychiatric and substance use disorders.
Findings First-degree relatives of opioid-dependent males were more likely to have a psychiatric disorder than those of normal controls [adjusted odds ratio (OR) 4.47; 95% confidence interval (CI) 1.97–10.11; P < 0.001], especially for opioid use disorders in the brothers (adjusted OR 6.55; 95% CI 1.44–29.88; P = 0.015) and for alcohol use disorders in the fathers of the probands (adjusted OR 5.64; 95% CI 2.39–13.24; P < 0.001). Other disorders (major depression, chronic psychosis and obsessive compulsive disorder) did not have significant aggregation in the first-degree relatives of opioid-dependent subjects.
Conclusions This study provides further evidence for the higher rates of alcohol and opioid dependence in first-degree relatives of opioid-dependent patients. The exact pattern of this familial aggregation may be influenced by the gender of the relatives and their relation to the proband.