So how come Bill Hicks was so funny?

Middle-aged and elderly men who smoke heavily are more likely to commit suicide, a major survey by the Japanese Ministry of Health, Labor and Welfare has found.

In an epidemiological survey conducted by a research team at the ministry, it was found that the rate of suicide among middle-aged and elderly men was linked to the number of cigarettes they smoked.

"We have to pay more attention to smokers' mental health," a representative of the research team said. The results will be announced at a meeting of the Japan Epidemiological Association in Otsu on Friday.

In 1990 and 1993, researchers investigated the habits of some 45,000 men aged between 40 and 69 living in eight prefectures in Japan including Iwate, Nagano, Kochi, Nagasaki and Okinawa. Follow-up investigations into their health were carried out up until 2000, and researchers investigated the relationship between smoking habits and 173 of the subjects who committed suicide during the period. A total of 108 of the 173 people who committed suicide were smokers. The rate of suicide among people who smoked less than 20 cigarettes per day was about the same as for nonsmokers, but the suicide rate of people who smoked between 30 and 39 cigarettes per day was 1.4 times higher than those in the group who smoked under 20 cigarettes a day.

The rate of suicide for those who smoked 40 or more cigarettes a day was 1.7 times higher. Researchers said no differences were seen based on the number of years people had been smoking.

A separate autopsy survey conducted by Kochi University last year found that among people who smoked, there was a higher concentration of nicotine in the blood of people who committed suicide than among those who died in accidents or because of illness.

Motoki Iwasaki, a scientist at the Epidemiology and Prevention Division of the National Cancer Center, said nicotine dependency was believed to increase the risk of depression. "The mechanism connecting smoking to suicide is not well understood, but there are research results showing that dependency on nicotine increases the risk of depression," he said. "Whether or not stopping smoking decreases that risk is a topic for future research." (Mainichi Shimbun, Japan, Jan. 18, 2005)