Rates Highest in
Spring, Summer Months
Despite reports of "winter blues" that appear to lift with the
first signs of spring, new findings show that people tend to commit
suicide more often during warmer months.
Australian researchers discovered
that, over a 10-year period, the rate of suicide peaked in spring
and summer and fell to its lowest level during winter months.
Suicide rates appeared to increase
with increasing hours of daylight, and showed no connection to
other meteorological factors such as changing temperature or rainfall.
The study could not determine why
there was an association between season and suicide. Previous
research has shown that longer periods of sunlight may increase
brain levels of serotonin, a chemical in the brain linked to depression.
Study author Dr. Gavin Lambert
said that he and his colleagues were initially surprised by their
findings, given that brain levels of serotonin appear to drop
during winter months.
However, he cautioned that depression
is a separate condition from seasonal affective disorder (SAD),
a regular recurrence of the blues that comes during the fall and
Depression and SAD "are two distinct
diagnostic conditions and I would anticipate that the brain neurochemistry
underlying the two is quite different," he said.
And despite the fact that serotonin
levels appear low in people with depression and depression is
linked to suicide risk, suicide itself may not result from low
serotonin in the brain, he said.
He noted that long periods of little
light during winter months may result in a prolonged dip in serotonin
levels, causing an increase in depression and suicidal behavior
that extends into the warmer months.
Pattern-breaking spikes in serotonin
following increases in daylight hours in the spring season may
result in "changes in volition or anxiety such as to trigger the
event," Lambert said, resulting in higher rates of suicide during
Lambert, who is based at Baker
Heart Research Institute in Melbourne, added that the study does
not suggest that keeping a suicidal person out of sunlight during
spring and summer is helpful.
People with depression -- who are
more at risk of suicide -- don't improve with bright light therapy,
he said, and restricting light will have no effect on the other
factors pushing people toward suicide.
"Of course, suicide results from
a multitude of factors (including) physical, mental -- if the
two can be separated -- and social," Lambert said. "Bright light,
by virtue of its impact on brain serotonin, is one piece of the
To investigate seasonal patterns
in depression and suicide, Lambert and his colleagues reviewed
meteorological changes and suicide rates in residents of the state
of Victoria, in Australia, between January 1990 and April 1999.
SOURCE: American Journal of Psychiatry
Reference Source 89