Influence of depression and early adverse experiences on illicit drug dependence: a case-control study

The purpose of this study was to investigate the association between depression and illicit drug dependence among a Latin-American population.

illicit drug dependent patients (n = 137) and controls (n = 274) were interviewed using the Diagnostic Interview for Genetic Studies, in order to detect lifetime and current depressive disorder and illicit (cocaine, cannabis or inhalants) substance dependence. A regression analysis was used to estimate the odds ratio for drug dependence according to the diagnosis of depression.

The lifetime diagnosis of depression (p = 0.001; OR = 4.9; 95% CI, 1.9-12.7) predicts illegal drugs dependence. Sociodemographic variables such as male gender (p < 0.001; OR = 36.8; 95% CI, 11.8-114) and occupational situation (p = 0.002; OR = 5.0; 95% CI, 1.8-13) as well as alcohol dependence (p = 0.01; OR = 3.4; 95% CI, 1.3-8.7) significantly influenced depression and drug dependence. Additional influent factors detected were having parents (p = 0.006; OR = 18.9; 95% CI, 2.3-158) or friends (p < 0.001; OR = 64.4; 95% CI, 6.5-636) who are illicit drugs dependents.

although a causal relationship between dependence on illicit drugs and depression cannot be determined, comparison of the sequence of events point to the occurrence of depression later in life than dependence. It remains to be determined whether depression is a comorbidity of dependence, sharing etiological factors, or a consequence of drug abuse and/or abstinence.