Conventional wisdom says we're gloomier when the weather's gross outside. But, new research suggests the opposite might be true: Sunnier days are correlated with more suicides.
The study, published this week in JAMA Psychiatry, used retrospective data compiling all recorded suicides in Austria from January 1, 1970 to May 6, 2010 — 69,462 suicides total. This data was then compared to weather patterns from that same time period. The researchers found a positive correlation between the average hours of sunshine and the average number of suicides in a day.
The study also looked at the correlation between the weather and the days leading up to a suicide. Their results showed that these deaths were more likely if there were up to 10 sunny days beforehand. But, if there were 14-60 sunny days, the correlation actually went in the opposite direction — suggesting that sunshine could either facilitate or protect against suicide, depending on the time frame.
Previous studies showed similar results, but this was the first one to use statistical differencing to rule out the established seasonal effects of sunshine and suicide. Although the study isn't saying that 10 days of sun will cause suicides, the researchers do suggest a biological reason for the link: changes in functioning of serotonin receptors. Serotonin is a neurotransmitter that is commonly associated with mood disorders, which are also commonly associated with suicide risk. Still, all of these pieces do not yet make a whole puzzle; there's no proof of causation, and it's not clear how serotonin modulation would translate to suicidal action.
Even though it might seem like a stretch to take these Austrian results and apply them to the rest of the world, the study authors note that Austria's climate is categorized as "humid continental" — just like the eastern U.S. and many central and eastern European countries. But, that doesn't mean that your SAD lamp is making you sad; it really just shows that suicide is a lot more complicated than we tend to think.