Smokers are more likely to commit suicide than those who never take up the habit – and the chemicals in cigarettes may be to blame.
Previous research has indicated that smokers are more likely to take their own lives – but it was thought this was because people with psychiatric disorders also tend to smoke.
Now new research suggests the nicotine in tobacco could trigger psychiatric disorders – or make them more severe.
The study compared U.S. states that have increased tobacco taxes and banned smoking in public to those that have not.
Those that had increased tobacco taxes and banned smoking in public places between 1990 and 2004 had saw suicide rates decline by up to 15 per cent compared to the national average.
Since, then states such as New York, Illinois and California have enforced smoking bans in public places.
The conclusions were drawn after analsying the different smoking policies adopted by different states, such as approaches to taxing cigarettes and limiting when and where people could smoke.
Using statistical methods, the researchers compared rates of suicide in states with stricter tobacco policies to rates in states with more lenient laws and lower taxes.
They say their findings show more policies to limit smoking should be introduced for mental health reasons as well as physical.
Richard Grucza, assistant professor of psychiatry at the university, said: ‘Although scientists have known for years that people who smoke have a higher risk for suicide, they had assumed the risk was related to the psychiatric disorders that affect many smokers.
‘These new findings, however, suggest smoking may increase the risk for psychiatric disorders, or make them more severe, which, in turn, can influence suicide risk.
‘We really need to look more closely at the effects of smoking and nicotine, not only on physical health but on mental health, too.
‘We don’t know exactly how smoking influences suicide risk. It could be that it affects depression or increases addiction to other substances. The numbers show it clearly does something.’
Nicotine is likely to be the key culprit, he added.
‘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.
‘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.
‘So the fact that we saw this influence among people who likely were smokers supports the idea that smoking itself is linked to suicide – rather than some other factor related to policy.
The research was published in the journal Nicotine & Tobacco Research.
This article first appeared on ‘Daily Mail’ on 17 July 2014.