Study Highlights

• This prospective cohort study included 3902 adolescents (58.0% female; 96.7% White) born between April 1, 1991, and December 31, 1992, to women in ALSPAC.
• At about ages 16, 18, 19, 21, and 23 years, alcohol dependence and consumption were measured with the self-reported AUDIT.
• At about ages 18, 21, and 23 years alcohol dependence and consumption were measured using items corresponding to Diagnostic and Statistical Manual of Mental Disorders, fourth edition, symptoms.
• Primary outcome was depression at age 24 years, using the Clinical Interview Schedule-Revised.
• Analyses were probit regressions between growth factors for alcohol dependence and consumption and depression, before and after adjustments for confounders: sex, housing tenure, maternal education and depressive symptoms, parents’ alcohol use, conduct problems at age 4 years, being bullied from age 12 to 16 years, and frequency of smoking cigarettes or cannabis.
• Using the estimated and observed means for alcohol consumption from age 16 to 23 years, at the start of the growth curve (age ~16.5 years), the average AUDIT-C score was 4.3.
• On average, the highest score of alcohol consumption was 6.0, at age ~20 years.
• After adjustments, alcohol dependence at age 18 years (latent intercept) was positively associated with depression at age 24 years (probit coefficient, 0.13; 95% CI, 0.02-0.25; P=.019).
• The association between alcohol dependence and depression at age 24 years was consistent across the developmental period of ages 17 to 22 years at each age of the growth curve.
• Rate of change of alcohol drinking (linear slope) was not associated with depression (0.10; 95% CI, −0.82 to 1.01; P=.84).
• After adjustments, alcohol consumption was not associated with depression (latent intercept probit coefficient, −0.01 [95% CI, −0.06 to 0.03; P=.60]; linear slope, 0.01 [95% CI, −0.40 to 0.42; P=.96]).
• When depression was regressed on levels of alcohol consumption or dependence at each age of the growth curve (17 to 22 years), there was no evidence for an association between alcohol consumption at any age with depression at age 24 years.
• Conclusions from sensitivity analyses were unchanged.
• The investigators concluded that there was evidence of a positive association between alcohol dependence at age 18 years and depression at age 24 years.
• Several potential mechanisms to explain this association are that alcohol dependence has physical, psychological, interpersonal, social, educational, and economic consequences that could lead to depression.
• Alcohol dependence may lead to antisocial behavior and cannabis use, which have been found to increase risk for subsequent depression.
• There was no evidence that frequency or quantity of alcohol consumption was associated with depression, but dependence and consumption were not directly compared.
• The findings therefore suggest that high frequency and quantity of alcohol consumption might not increase the risk for depression during young adulthood unless there are also features of dependency involved.
• There was no evidence that a faster increase in levels of dependence across adolescence was associated with depression at age 24 years, and only small variability in rate of change over time, suggesting that the magnitude of the association between dependence and depression is fairly constant over adolescence.
• Therefore, the specific timepoint for considering levels of alcohol dependence between ages 16 and 23 years -- a developmental period when average alcohol use increases rapidly -- might not be particularly important.
• Psychosocial or behavioral interventions to lower risk for alcohol dependence during adolescence, or potentially treating it early, may contribute to preventing depression in young adulthood, which could have important public health implications.
• However, heavy alcohol consumption is likely to precede dependence.
• It therefore remains important to prevent or reduce high frequency and quantity of alcohol drinking during adolescence, especially given its associations with other harms, including injury and antisocial behavior; this could reduce the risk for future dependence and physical health problems.
• Public health interventions to prevent depression among youth could target subthreshold levels of alcohol dependence, which are likely to involve high frequency and quantity of consumption.
• Public health messages aimed at young people to prevent depression could emphasize dependent aspects of drinking that are especially harmful.
• Study limitations include substantial attrition in the ALSPAC cohort from birth to age 24 years; that the sample was recruited from 1 UK region and had predominantly White participants, limiting generalizability; use of measures of alcohol consumption and dependence that excluded some features of abuse; and observational design with potential for residual confounding.