I don't know how common this factor is, but maybe it should be
considered. And maybe there are limits of low bmi to some people.

Here's several different citations, the first reports from Sweden (in
pubmed) and the second from the New York Times.

Am J Epidemiol. 2006 Jan 1;163(1):1-8. Epub 2005 Nov 3.

Association of body mass index with suicide mortality: a
prospective cohort study of more than one million men.

Department of Genetics and Pathology, Uppsala University, Uppsala,
Sweden.

The authors investigated the association of body mass index (BMI)
with suicide in a record linkage study based on the Swedish Military
Service Conscription Register, the Population and Housing Censuses,
and the Cause of Death Register. The cohort studied consisted of
1,299,177 Swedish men who were conscripted in 1968-1999, had their BMI
measured at age 18-19 years, and were followed up for as long as 31
years. A strong inverse association was found between BMI and suicide.
For each 5-kg/m2 increase in BMI, the risk of suicide decreased by 15%
(95% confidence interval: 9, 21). The association was similar when
subjects with mental disorder at baseline were excluded from the
analysis. BMI-suicide associations were similar in relation to suicide
deaths occurring in the first 5 years of follow-up (hazard ratio for
each 5-kg/m2 increase in BMI = 0.84, 95% confidence interval: 0.73,
0.96) compared with associations or = 10 years after baseline
(hazard ratio = 0.87, 95% confidence interval: 0.79, 0.96), indicating
that weight loss as a consequence of mental illness does not explain
the BMI-suicide association and that factors influencing BMI may be
causally implicated in the etiology of mental disorders leading to
suicide.

PMID: 16269577 [PubMed - indexed for MEDLINE]

The next is from the NY Times dated March 13, 2007

http://www.nytimes.com/2007/03/13/he...0A&oref=slogin

"...In a 16-year study that followed more than 45,000 male health
professionals, researchers found a steady decrease in suicides as
B.M.I. increased, even after controlling for variables including
smoking, dietary factors, physical activity, marital status and
alcohol use. There were 131 suicides during the time of the study.

"Compared with those in the lowest 20 percent in B.M.I., men in the
highest one-fifth were almost 60 percent less likely to kill
themselves.

"It's a surprisingly strong relationship," said Kenneth J. Mukamal,
the lead author and an associate professor of medicine at Harvard
University. "But even though we see that heavier men are less likely
to commit suicide, there are plenty of other studies that link obesity
to poor health. Gaining weight is not the best way to improve anyone's
mental health. I hope these findings will provide insight into new
strategies to prevent suicide."

"The authors, writing in The Archives of Internal Medicine, suggest
that B.M.I. could be linked to suicide through circulating levels of
insulin, which may have a role in determining mood."

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I don't know if there is a pattern for females but it is interesting.

Yours,

Caleb