Suicide Rates Highest in
Spring, Summer Months
Excerpt By Alison McCook, Reuters Health

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 winter.

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 longer days.

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 puzzle."

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 2003;160:793-795.

Reference Source 89

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