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 People shouldn’t avoid the sun based on the study’s findings, says
its senior author. Instead, they may consider adding sunshine to the
list of factors that may influence the risk of suicide.
“Suicide is complicated and has many risk factors,” said Dr.
Matthaeus Willeit from the University of Vienna.
“People always tend to think of it in either biological or social
terms, but there is no single cause,” he said. “It’s a bunch of risk
factors that you have. That is just one of many risk factors.”
Researchers have studied seasonal variations among suicides for
centuries, with rates peaking in the spring. The actual effect of
sunshine on those rates is less known, though. Along with changes in
sunlight, new seasons bring temperature changes and a number of
other factors that may influence suicide risk, such as holidays.
For the new study, the researchers used information on 69,462
suicides that occurred in Austria between January 1970 and May 2010.
That data was then matched to data collected from 86 weather
stations that recorded the hours of sunshine per day.
The researchers found a correlation between the number of suicides
per day and the amount of sunshine throughout the study.
After adjusting the numbers to account for seasonal variations in
suicides, they found that suicide risk went up with the amount of
sunshine over the previous 10 days. Suicide risk appeared to
decrease with increasing sun exposure between 14 to 60 days earlier,
however.
The researchers suggest that sunlight may increase the risk of
suicide over a short period but actually protect against it over a
longer period of time. They can’t definitively say sunlight causes
or prevents suicides, however.
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It could be that sunlight affects serotonin in the body, they say.
Serotonin then may influence impulsivity, mood and aggression, which
can play a role in suicidal behavior.
Sunlight may act like antidepressant medications that affect
impulsivity first and then mood later on. The early affect on
impulsivity may explain the increased suicide risk over a short
period of time, and the delayed affect on mood may explain the lower
risk over a longer time span.
“Light has an influence on serotonin and serotonin has an influence
on mood and suicidality,” Willeit said. “That’s probably one of the
biological links.”
Alternatively, he and his colleagues write in JAMA Psychiatry, the
early increased risk of suicide after sun exposure may lead to those
most at risk to take their own lives. Fewer of the most at-risk
people would then be susceptible to sun exposure later on.
As for right now, Willeit said that the study can’t instruct doctors
what to tell their patients based on weather reports.
“In the long term it would be great to know whose risk really
increases with light,” he said.
SOURCE: http://bit.ly/YEeDwT JAMA Psychiatry, online September 10,
2014.
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