WEDNESDAY, July 16, 2014 (HealthDay News) -- Smoking may increase a person's risk for suicide, but high cigarette taxes and smoking restrictions in public places lower that risk, a new study suggests.
Previous research has found that smokers are more likely to take their own lives than nonsmokers. This difference was attributed to the fact that smoking is common among people with psychiatric disorders, who have higher suicide rates.
However, this new study suggests that smoking itself may increase suicide risk and that efforts to reduce smoking may lead to lower suicide rates.
"Our analysis showed that each dollar increase in cigarette taxes was associated with a 10 percent decrease in suicide risk," study leader Richard Grucza, associate professor of psychiatry at Washington University School of Medicine in St. Louis, said in a university news release. "Indoor smoking bans also were associated with risk reductions."
For the study, published online July 16 in the journal Nicotine & Tobacco Research, Grucza and his colleagues analyzed suicide rates across the United States between 1990 and 2004. During this period, some states introduced aggressive anti-smoking policies while others did little or nothing to reduce smoking.
Nationally, an average of 14 per 100,000 people commit suicide every year.
The study found that states that introduced higher taxes on cigarettes and stricter rules to limit smoking in public places saw suicide rates decline up to 15 percent, relative to the national average.
In states that had lower cigarette taxes and did little to limit smoking in public, suicide rates increased by up to 6 percent, compared to the national average.
"States started raising their cigarette taxes, first as a way to raise revenue but then also as a way to improve public health," Grucza said.
Higher taxes and more restrictive smoking policies are well-known ways of getting people to smoke less, he added. "So it set a natural experiment, which shows that the states with more aggressive policies also had lower rates of smoking. The next thing we wanted to learn was whether those states experienced any changes in suicide rates, relative to the states that didn't implement these policies as aggressively," he explained.
In 2010, nearly 40,000 people in the United States committed suicide, according to the Centers for Disease Control and Prevention. Suicide is the 10th leading cause of death in the nation.
"If you're not a smoker, or not likely ever to become a smoker, then your suicide risk shouldn't be influenced by tobacco policies," Grucza said. "So the fact that we saw this influence among people who likely were smokers provides additional support for our idea that smoking itself is linked to suicide, rather than some other factor related to policy."
It's not clear how smoking affects suicide risk, but it's highly likely that nicotine is a factor, the researchers said.
"Nicotine is a plausible candidate for explaining the link between smoking and suicide," Grucza said. "Like any other addicting drug, people start using nicotine to feel good, but eventually they need it to feel normal. And as with other drugs, that chronic use can contribute to depression or anxiety, and that could help to explain the link to suicide."
Although states with stricter anti-smoking regulations saw suicides decline, the study doesn't prove a direct cause-and-effect relationship.
The U.S. Centers for Disease Control and Prevention has more about suicide prevention.