Australian researchers have found that women who smoke are more likely to develop a major depressive disorder than women who don’t smoke.

A total of 671 women with no history of major depressive disorders were studied. Of the 87 women who were smokers, 13 (15%) went on to develop major depressive disorder.

However, among 584 non-smokers, just 38 (6.5%) developed major depressive disorder during a decade of follow-up.

Heavy smokers, those who smoke more than twenty cigarettes a day, are twice as likely to become depressed than more moderate smokers.