While Americans worry about whether cigarette smoking will cause lung
cancer, perhaps they should also pay attention to a lesser-known risk factor
for the habit—suicide. Epidemiological studies going back at least a
quarter century have linked cigarette smoking with suicide. And now another
large epidemiological study does as well.
This latest investigation was headed by Naomi Breslau, Ph.D., a professor
of epidemiology at Michigan State University. Results appeared in the March
Archives of General Psychiatry.
In 1988, Breslau and her colleagues selected some 1,000 young adults to
participate in their study. All were members of a health maintenance
organization in the Detroit area. All were interviewed at baseline and at
three, five, and 10 years after the study started. During each interview,
their psychiatric health, smoking habits, and occurrence of suicidal thoughts
and of suicidal attempts since the last interview were ascertained.
As it turned out, subjects reported only 19 suicide attempts during the
10-year study period. Since 19 suicide attempts were not enough for a
meaningful statistical analysis, Breslau and her team decided to lump suicidal
attempts and suicidal thoughts together. Combining these gave 17 suicide
attempts with the reporting of suicidal thoughts; two suicide attempts without
the reporting of suicidal thoughts; and 130 suicidal thoughts without suicide
attempts, for a total 132 suicidal thoughts and/or attempts.
Breslau and her colleagues then attempted to see whether smoking at
baseline, at the three-year assessment, and at the five-year assessment could
be statistically linked with the combined number of suicidal thoughts or
attempts during the subsequent study periods.
The answer was yes. Compared with subjects who had never smoked, current
smokers (those who had smoked during the past 12 months) were at a
statistically significant increased risk of suicidal thoughts or attempts. In
contrast, past daily smokers were not at increased risk for subsequent
occurrence of suicidal thoughts or attempts.
Moreover, this link between current cigarette smoking and suicidal thoughts
or attempts held even when potentially confounding factors—prior
suicidal thoughts or attempts, current or past major depression, and current
or past substance abuse—were taken into consideration.
And even though the study results did not find current cigarette smoking to
be as grave a risk factor for suicidal thoughts or attempts as prior suicidal
thoughts or attempts, or current or past major depression, they do suggest
some practical implications.
"Clinical psychiatrists should always be concerned and inquire about
suicidality, self-destructive thoughts, et cetera," Glenn Davis, M.D., a
professor of psychiatry at Michigan State University and one of the study
authors, said in an interview. "But with added knowledge that there is a
connection between smoking and risk for suicidal behavior, they should be
particularly sensitive to smoking history in their evaluation of
"By highlighting current smoking, [this study further reinforces] the
benefits of smoking cessation," Donald Klein, M.D., a professor of
psychiatry at Columbia University, pointed out to Psychiatric
How current cigarette smoking might trigger suicidal thoughts or attempts
is not known. Yet if it does play a causal role, Breslau and her team suspect
that it may do so via an intermediary culprit—the enzyme monoamine
oxidase (MAO), which is found in the liver and the central nervous system. It
is crucial to the functions of the neurotransmitter serotonin. Low levels of
MAO have been found in blood cells of current cigarette smokers, but not in
those of ex-smokers, and low blood-cell levels of MAO in turn have been linked
with violence and suicide.
This investigation has several advantages over past ones on the subject. It
took major depression, a well-established risk factor for suicide, into
consideration, and it was quite sophisticated in design. Klein explained that
it "incorporated major methodological advances by using prospective
multiwave longitudinal psychiatric diagnoses in estimating whether smoking
independently increases suicide-related behaviors."
The study had a weakness, however, which Breslau and her group acknowledged
in their report: The researchers did not gather data about subjects' completed
suicides, only about their suicidal thoughts and attempts.
The study was funded by the National Institute of Mental Health.
An abstract of "Smoking and the Risk of Suicidal
Behavior" is posted online at<http://archpsyc.ama-assn.org/cgi/content/abstract/62/3/328>.▪
Arch Gen Psychiatry200562328