Researchers debunk myth that alcohol causes depression

Alcohol has been cleared as a potential cause of depression. Clinical neuroscientists at the University of Western Australia have concluded that there is no truth to the long held belief which holds that alcohol causes depression, particularly if consumed at excessive levels.

“Even one of the diagnoses we have for depressive disorders - substance induced mood disorder - is a diagnosis where alcohol plays a role,” said Professor Osvaldo Almeida from the University’s School of Psychiatry and Clinical Neurosciences.

“However, because of the observational nature of the association between alcohol and depression, and the risk of confounding and bias that comes with observational studies, it is difficult to be entirely certain that the relationship is causal.

“For example, people who drink too much may also smoke, have poor diets and other diseases that could explain the excess number of people with depression among heavy drinkers.”

Professor Almeida and fellow researchers involved in the Health in Men Study (HIMS) searched for a causal link via physiological pathways - specifically, the genetic polymorphism, or mutation, most closely associated with alcohol metabolism.

Certain genetic variations affect the amount of alcohol people consume, Professor Almeida said. One particular variation produces an enzyme that is 80 times less effective at breaking down alcohol; people with this variation are much less tolerant to alcohol than others. Recent research shows that alcohol-related disorders are very uncommon in people with this variation.

“Now, if alcohol causes depression, then a genetic variation that reduces alcohol use and alcohol-related disorders should reduce the risk of depression,” said Professor Almeida. “The great advantage of looking at this gene is that this association is not confounded by any other factors - people are born like that.”

Analysing the triangular association between the genetic mutation, alcohol and depression in HIMS participants, the researchers found that this particular genetic variant was associated with reduced alcohol use, but had no association with depression whatsoever.

“The conclusion is that alcohol use neither causes nor prevents depression in older men,” Professor Almeida said. “Our results also debunk the view that mild to moderate alcohol consumption may reduce the risk of depression.”

The association between alcohol and depression was likely explained by other factors, but not by alcohol itself, Professor Almeida said.

“It doesn’t mean alcohol is entirely safe and people can consume it in whatever way they like. We know that alcohol when consumed in excess does create a lot of health problems - but what we now know is that one of these problems is not depression.

A paper on the study - The triangular association of ADH1B genetic polymorphism, alcohol consumption and the risk of depression in older men - was published in the journal Molecular Psychiatry.