New research suggests that exposure to sunshine affects suicide rates, regardless of what time of year it is.

Published in JAMA Psychiatry, the study looked at the relationship between daily suicide rates — 69,462 over 40 years — and hours of daily sunshine independent of season. The study linked higher rates of suicide with shorter durations of sunny weather — 10 days or fewer — regardless of season, says Norman Sussman, MD, professor of psychiatry and director of the Treatment Resistant Depression Program at NYU Langone Medical Center, who was not involved in the study.



The researchers also found that longer periods of sunshine — 14 to 60 days — had a protective effect that resulted in lower rates of suicide.

The new study differs from earlier ones that found seasonal patterns to U.S. suicide rates, with the highest in the spring and lowest during winter months.

Weather-Suicide Connection  

So why does sunshine affect suicide rates? “There are hormonal changes that are triggered by the sunshine, with a circadian rhythm aspect to it. A lot of that drives what happens in mental disorders,” says Dr. Sussman. Previous research shows that light interacts with brain serotonin systems in people, and that may affect serotonin-related behaviors like mood and impulsiveness.

“I think the sunshine gives people the energy to go through with their plan,” says Everyday Health Sanity Break blogger Therese Borchard. “In winter months, sometimes people are too depressed to actually commit suicide, but with the sunlight comes a spark of energy needed to follow through with the plan.”

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Another theory is that poor, unfavorable weather is consistent with the mood of a person experiencing suicidal ideations.


“Conversely, when it’s sunny out, people see this discordance that everyone is outside having a good time, and you’re down in the dumps,” Sussman says. “This conscious contradiction of how you’re feeling and what everyone else is doing could play a role.”

Implications for Treatment

Sussman emphasizes that suicides aren’t predictable. “Even the best psychiatrists cannot with absolute certainty predict if someone will commit suicide.” However, he says doctors look for certain things when treating a patient with suicidal ideations including how long a person has been depressed, family history of suicide, and how long the patient has been treated without improvement. He says mental health professionals should also consider weather changes when treating patients.
“If someone is suicidal, and if they’re being seen by a psychiatrist, and suddenly the weather changes and it’s really sunny, I would say whoever is treating that person should ask if they are feeling more suicidal. This study suggests we should include weather as part of screening for patients who are depressed,” says Sussman.


Borchard recognizes that there’s a connection between her symptoms and the weather. “I feel symptoms of hypomania as the sun starts to shine more in spring. Sometimes the hypomania could make a person complete suicide.” However, she adds that generally she does feel better with sunshine.

Future research should identify the patients most vulnerable to the suicide-triggering effects of sunshine, recommend the study’s authors.
Still, says Sussman, suicides are unpredictable. “Most suicides are really impulsive. It can take less than 12 seconds from the thought to act.”