Surprisingly, suicides increase in the spring, rather than in the winter. In a paper published on Wednesday in the Journal of the American Medical Association Society Psychiatry (JAMA Psychiatry), researchers argue that sunshine is linked to fatal self-harm, independent of the season.

They studied suicide data from Statistics Austria, from January 1970 to May 2010 alongside meteorological data for the same time period.

Of the 69,462 suicides registered in Austria during that 40-year period, they found that days with more suicides tended to be sunnier. And surprisingly, a run of sunny days often ended in tragedy.

“The amount of light approximately two weeks before a suicide event is positively correlated with suicide. The more light you have in a certain period, probably short-ranging, the more likely a person who is already at risk is to commit suicide,” said Dr Matthaeus Willeit, a professor at the Medical University of Vienna and the study’s senior author.

Sunlight exposure is related to serotonin levels in the brain. Whilst the 'mood' hormone serotonin generates happiness, it is also associated with impulsivity.

So someone already thinking about suicide may be triggered into an impulsive action by exposure to short bursts of sunlight and serotonin.

However, longer periods of sunshine seems to have a “protective effect” – elevating moods in a way that are sustainable for a longer time period.

Willeit said that his team plans further research on the relationship between light and the serotonin system.