A large-scale longitudinal study has confirmed a link between current smoking habits and risk for suicidal thoughts and attempts, although the mechanism underlying the association of current smoking habit as an independent predictor of suicide is unclear, according to an article in the March issue of the Archives of General Psychiatry.

A link between cigarette smoking and suicide has been reported in epidemiological investigations since the 1970s, according to background information in the article. However, these interpretations have been subject to controversy. It is believed that depression may result in part from smoking and should not be controlled in analysis of this relationship. However, it has also been reported that symptoms of depression in adolescents predicts their starting smoking and that major depression leads to an increased risk for regular smoking and dependence; therefore, a history of depression must be considered when examining suicide in smokers.

Naomi Breslau, PhD, and her American colleagues examined the association between cigarette smoking and suicidal thoughts and attempts. Participants aged 21 to 30 years were interviewed in 1989 and completed follow-up interviews in 1992, 1994, and 1999 - 2001. At each assessment, they were asked about lifetime smoking history, whether they were current daily smokers or had been in the past, and psychiatric disorders. Nearly nine hundred people completed all three investigations.

During the ten-year follow-up, 19 participants attempted suicide, while 130 reported having suicidal thoughts. The researchers found that current daily smoking, but not past smoking, as reported at the beginning of each of the assessment periods, predicted the subsequent occurrence of suicidal thoughts or attempt.

These findings remained when adjusted statistically for prior depression, substance use disorders, prior psychiatric disorders and prior suicidal disposition. Rates of suicidal behavior were also higher in those experiencing depression at the start of each follow-up period.