The nature of the relationship between alcohol abuse and depression is controversial. Now a modeling study suggests that alcohol abuse leads to depression, not the other way round.

Summary

That there is a link between alcohol abuse and depression has long been clear. But it has not been known whether alcohol triggers depression, or whether depression causes people to self-medicate with alcohol. These findings could lead to more effective ways of helping people with alcohol problems.

Introduction

Alcohol abuse and depression often go hand-in-hand. But the nature of the relationship has been difficult to tease out, because both alcoholic and depressive behavior are complex. It could be that some underlying factor, such as stress or genetics, predisposes people towards misusing alcohol and depressive illness. Or it may be that depressed people turn to alcohol to boost their mood. The other possibility is that alcohol misuse leads to depression. A better understanding of the link between alcohol abuse and depression could help those suffering from these complex disorders.

What was done

Researchers from the Christchurch School of Medicine, New Zealand, worked with data from a group of 1,055 participants born in 1977. They were asked about both alcohol abuse and depression at the ages of 17-18, 20-21 and 24-25 years.

What was found

At ages 17-18, 19.4% suffered alcohol problems and 18.1% major depression. The figures at 20-21 were 22.4% and 18.2% respectively. And by 24-25, the figures had diminished somewhat to 13.6% and 13.8%. Therefore, around one in five of these young people had either an alcohol disorder, major depression or both. Those who fulfilled criteria for alcohol abuse or alcohol dependence were almost twice as likely to suffer major depression compared to those free of alcohol problems. The researchers tested three models to try to establish the nature of the relationship between alcohol and depression. The model supporting the notion than alcohol use leads to depression fitted the data best. Therefore, it seems that alcohol abuse comes first, then depression - not the other way round.

What this study means

This research does not reveal why alcohol abuse leads to depression. The researchers suggest that maybe alcohol uncovers some genetic disposition to depression in some people. Or the stress and problems caused by alcoholism might lead to depression. Alcohol itself may act on the brain to trigger depression. A better understanding of how alcohol abuse leads to depression will be useful in helping people manage alcohol problems.

Source

Tests of causal links between alcohol abuse and major depression D. Fergusson,  et al, Archives of General Psychiatry, March 2009, vol. 66, pp. 260--266