Women who smoke at risk for major depression

A new study by Australian scientists has revealed that women who smoke are at greater risk of developing a major depressive disorder.

The link between depression in women and smoking was found as a result of a decade long study by researchers from the University of Melbourne and Barwon Health, Victoria's largest regional health service.

The longitudinal study involved 1,043 Australian women, whose health had been monitored for a decade as part of the Geelong Osteoporosis Study - at a ten year follow up the participants underwent an additional psychiatric assessment.

Lead researcher, Associate Professor Julie Pasco, who led the study within the Clinical and Biomedical Sciences at Barwon Health, says it was at this point that they were able to determine if depression had developed and investigate whether or not smoking pre-dated the onset of depression.

The results revealed that compared with non-smokers, the likelihood for developing depression more than doubled for heavy smokers (those who smoked more than 20 cigarettes a day) and women with depression were more likely to have been smokers than those without depression.

The researchers also examined the data to determine the risk of women developing a new major depressive disorder over time.

A total of 671 women with no history of major depressive disorders were studied and of the 87 smokers, 13 (15%) went on to develop major depressive disorder - among the 584 non-smokers, just 38 (6.5%) developed major depressive disorder during a decade of follow-up.

Professor Pasco says this indicates that non smokers were at a lower risk for developing major depression and suggests that smoking may play a role in the development of the disease in women.

The researchers say previous research has also shown that smoking is a risk factor for depression and say there is also increasing evidence that smoking may aggravate mental illness or contribute to its onset.

However these studies have usually involved short time frames - while this study is the first to investigate smoking using longitudinal data that extends over a ten-year period.

The researchers say that as depression is a leading contributor to the global disease burden, greater efforts to encourage smokers to quit are called for.

Experts say that smoking may possibly trigger depression by upsetting the activity of dopamine, a brain chemical linked to addiction and depression, which has implications for a number of psychiatric illnesses such as schizophrenia and bi-polar disorder.

They suggest that smoking might increase the likelihood of depression because it also produces tissue-damaging compounds called free radicals.

The research is published in The British Journal of Psychiatry.