#depression #suicide - Sunshine directly influences suicide incidence, according to a new study.

The amount of daily sunshine individuals receive appears to have a direct impact on suicide incidence, new research suggests. A large, retrospective analysis of all officially confirmed suicides in Austria shows that the number of hours of daily sunshine and the number of daily suicides during a 40-year period were "highly correlated."

Researchers found there was a positive correlation between the number of suicides and hours of daily sunshine on the day of the suicide and up to 10 days before that seemed to facilitate suicide; sunshine occurring 14 to 60 days prior was associated with a reduction in suicides. The study was published online September 10 in JAMA Psychiatry.

The investigators point out that light interacts with brain serotonin systems and may influence serotonin-related behaviors, including mood and impulsiveness, which can play a role in suicide.

The study included data on 69,462 officially confirmed suicides in Austria between January 1970 and May 2010. Hours of sunshine per day were calculated from 86 representative meteorologic stations. Results revealed that the duration of sunshine influenced suicide rates independently of seasonal rhythms, the investigators report. Moreover, they show that sunshine has a bimodal effect on suicidal behavior as an increase in suicide was found in short time scales, while after longer periods more sunshine was associated with decreased suicide. Further research is warranted to determine which patients with severe episodes of depression are most susceptible to the suicide-triggering effects of sunshine.