Answers Sought for Link Found Between Smoking, Increased Suicide Risk

Chronic smoking may be an independent cause of increased suicide risk.

An analysis of data comparing suicide decedents with accident and homicide decedents found that longer lifetime smoking was associated with increased odds of death by suicide, while quitting smoking and longer periods of abstinence were associated with lower odds of dying by suicide. The results were significant only in males.

The findings were published October 1 in Psychiatric Services in Advance.

“Smoking is a form of self-medication that is addictive,” lead researcher Lloyd Balbuena, Ph.D., M.S., of the Department of Psychiatry at the University of Saskatchewan, told Psychiatric News. “In the very short term, smoking improves mood, but in the long run … smoking worsens mood and impairs cognitive function. It is not far-fetched to believe that with these challenges, the person is more vulnerable to stressors that could otherwise be handled more easily.”

Balbuena and co-author Raymond Tempier, M.D., of the Department of Psychiatry at the University of Ottawa used data from the 1993 U.S. National Mortality Followback Survey. The survey involved a nationally representative sample of 22,957 individuals aged 15 and older who died in 1993; in 1998, data from coroners’ reports on cause of death were added to the 1993 data, including natural, accidental, suicide, and homicide deaths.

The data included information on lifetime smoking duration, history of ever quitting smoking, and duration of abstinence from smoking. Also included was a “psychological autopsy” that was drawn from interviews with next of kin to collect information on history of depressive disorders, alcohol consumption or drug use, living alone in the last year of life, and keeping a firearm—all potential risk factors for violent death. Veteran status was obtained from the death certificate.

Balbuena and Tempier found that male suicide decedents smoked for a larger fraction of their lives compared with decedents in the control groups, were less likely to have quit smoking in their lifetime, and abstained from smoking for a smaller fraction of their lives. Specifically, males who smoked for a total of at least 41 years had higher odds of dying by suicide than did male smokers who smoked for 10 years or less. And a history of having a period of abstinence from smoking of at least 11 years in duration was associated with lower odds of suicide than smokers who had quit for five years or less.

The same associations were not found among females. “Males and females differ in their ways of seeking help for mental health problems,” Balbuena said. “It is possible that female smokers seek professional help more than their male counterparts, and in doing so are less at risk for suicide. Additionally, the impact of risk factors for suicide typically differs by gender. It is possible that smoking combines with other male-specific risk factors contributing to suicide.”

Also, he said that it is possible that next-of-kin reporters might also give different accounts depending on the gender of the decedent.

But the results linking smoking history to suicide remained true for males even when controlling for potential confounders. “This implies that smoking is independently associated with suicide,” they said. “However, this interpretation needs to be tempered by the fact that our measures were imperfect and the study had a retrospective design. Thus, a causal relationship cannot be inferred.”

In their report, the authors speculated that chronic nicotine exposure can cause a reduction in serotonin metabolites and that the frontal cortex becomes less receptive to serotonin. “Psychologically, smoking can worsen factors that predispose to suicide, such as increased mood lability, irritability, and depressed feelings, as well as behavioral tendencies such as aggression and impulsivity, which are known predictors of suicide,” they noted.

In comments to Psychiatric News, Balbuena pointed out that suicide is a rare outcome, and national databases recording this outcome are rarer still. “We would love to have access to a database of genetic data to examine which genes are turned on and off by smoking,” he said. “If this database could somehow be linked to a deaths register, that would provide evidence one way or the other to our research question.”

He added that for clinicians, the “take home” message is early prevention. “Smoking typically starts in adolescence,” he said. “Youth presenting to clinicians for general mental issues should be asked about their smoking behavior. Parents of these adolescents can be advised to monitor their mood.” ■