Is There a Causal Link between Alcohol Abuse or Dependence and Depression?
There is known comorbidity between alcohol abuse or dependence (AAD) and major depression (MD). Nevertheless, it is unclear whether AAD increases the risk of MD or vice versa. Using data from a 25-year longitudinal study of a birth cohort from New Zealand (1055 of 1265 subjects had follow-up data at ages 17–18, 20–21, and 24–25 years) and advanced statistical modeling techniques, the authors determined the association between AAD and MD and explored its causal direction.
- The prevalence of AAD and MD, respectively, was
- 19.4% and 18.2% at age 17–18;
- 22.4% and 18.2% at age 20–21; and
- 13.6% and 13.8% at age 24–25.
- There was a significant association between AAD and MD at all ages and for both genders: subjects with AAD were 1.9 times more likely to also have MD.
- The association remained significant when adjusted (using advanced statistical techniques) for nonobserved genetic and environmental factors and for variables that change over time (e.g., stressful life events, cannabis use, illicit drug use, affiliation with deviant peers, unemployment, partner substance use, and criminal offending).
- Results suggested a unidirectional association from AAD to MD but no reverse effect on MD to AAD.
Comments:This study points out a possible cause and effect relationship in which AAD leads to MD. This is not consistent with previous studies. Even though the study is based on longitudinal data, results rely on the assumptions of advanced statistical modeling techniques that are not widely or easily understood. The question of the causal relationship between AAD and MD remains open, but these results do suggest that alcohol abuse or dependence may lead to major depression. Nicolas Bertholet, MD, MSc
Fergusson DM, Boden JM, Horwood LJ. Tests of Causal Links Between Alcohol Abuse or Dependence and Major Depression. Arch Gen Psychiatry. 2009;66(3):260–266.