The surprising link between sunshine and suicide

Lengthening daylight isn't necessarily good news where mental health is concerned.

Gary Hershorn/Getty Images

Studies dating back to the 1800s have found that suicides peak in the spring and are lowest in winter.


“If we take winter as a baseline, then there's a 20–60 per cent higher suicide rate during spring," says Fotis Papadopoulos, a professor of psychiatry at Uppsala University in Sweden, who has been studying the association.

This seems rather counterintuitive considering that darker days are linked to low mood. How could this be? One possibility is that this is a result of changing levels of serotonin – a neurotransmitter that regulates mood – within the brain. Studies have found that serotonin levels in the blood are higher during the summer than the winter, and that there's a positive correlation between serotonin synthesis and the hours of sunshine on the day that a blood sample is taken.

There's also a further connection, in that selective serotonin reuptake inhibitor (SSRI) antidepressants, which boost serotonin, have been linked to risk of suicide in a small number of patients. “We know that when we treat patients with antidepressants it can take at least three or four weeks to raise their mood," says Papadopoulos. “During this time, some people become more physically active or agitated, which could potentially make them more likely to act on their thoughts. Maybe sunshine acts in a similar way in a minority of people."

Papadopoulos has scrutinised forensic and meteorological data for more than 12,000 suicide victims, and has found that there is a link between monthly sunshine duration and suicide risk – but this link disappears in most people when the season in which the data was collected is factored in. That said, the association remains in people who were taking antidepressants at the time of death. “It could be interpreted as support for the serotonergic theory," Papadopoulos says.

There are other theories, such as the release of pollen-triggered immune responses that bring about changes in brain chemistry. "It's a far-fetched idea that the romantic life of trees could be linked to suicidal behaviour in humans, but we have found an association between high tree pollen and non-violent suicides in women," says Teodor Postolache, a professor of psychiatry at the University of Maryland School of Medicine. There is also evidence linking cytokine therapies – which alter the behaviour of immune cells – to suicide ideation in a small number of patients, he says.

The link between sunlight and suicide is far from clear, and – it must be stressed – would only affect a minority of people. But given that antidepressant drugs are a far from perfect treatment and that we still don't fully understand depression, mood or our relationship with sunlight levels, it's an area worthy of further study.

For details of the suicide prevention centres in a particular country, visit the International Association for Suicide Prevention's website.

Studies dating back to the 1800s have found that suicides peak in the spring and are lowest in winter. "If we take winter as a baseline, then there's a 20–60 per cent higher suicide rate during spring," says Fotis Papadopoulos, a professor of psychiatry at Uppsala University in Sweden, who has been studying the association.

This seems rather counterintuitive considering that darker days are linked to low mood. How could this be? One possibility is that this is a result of changing levels of serotonin – a neurotransmitter that regulates mood – within the brain. Studies have found that serotonin levels in the blood are higher during the summer than the winter, and that there's a positive correlation between serotonin synthesis and the hours of sunshine on the day that a blood sample is taken.

There's also a further connection, in that selective serotonin reuptake inhibitor (SSRI) antidepressants, which boost serotonin, have been linked to risk of suicide in a small number of patients. "We know that when we treat patients with antidepressants it can take at least three or four weeks to raise their mood," says Papadopoulos. "During this time, some people become more physically active or agitated, which could potentially make them more likely to act on their thoughts. Maybe sunshine acts in a similar way in a minority of people."

Papadopoulos has scrutinised forensic and meteorological data for more than 12,000 suicide victims, and has found that there is a link between monthly sunshine duration and suicide risk – but this link disappears in most people when the season in which the data was collected is factored in. That said, the association remains in people who were taking antidepressants at the time of death. "It could be interpreted as support for the serotonergic theory," Papadopoulos says.

There are other theories, such as the release of pollen-triggered immune responses that bring about changes in brain chemistry. "It's a far-fetched idea that the romantic life of trees could be linked to suicidal behaviour in humans, but we have found an association between high tree pollen and non-violent suicides in women," says Teodor Postolache, a professor of psychiatry at the University of Maryland School of Medicine. There is also evidence linking cytokine therapies – which alter the behaviour of immune cells – to suicide ideation in a small number of patients, he says.

The link between sunlight and suicide is far from clear, and – it must be stressed – would only affect a minority of people. But given that antidepressant drugs are a far from perfect treatment and that we still don't fully understand depression, mood or our relationship with sunlight levels, it's an area worthy of further study.

For details of the suicide prevention centres in a particular country, visit the International Association for Suicide Prevention's website.

This article first appeared on Mosaic and is republished here under a Creative Commons licence.

Yug, age 7, and Alia, age 10, both entered Let Grow's "Independence Challenge" essay contest.

Photos: Courtesy of Let Grow
Sponsored by Charles Koch Foundation
  • The coronavirus pandemic may have a silver lining: It shows how insanely resourceful kids really are.
  • Let Grow, a non-profit promoting independence as a critical part of childhood, ran an "Independence Challenge" essay contest for kids. Here are a few of the amazing essays that came in.
  • Download Let Grow's free Independence Kit with ideas for kids.
Keep reading Show less

Four philosophers who realized they were completely wrong about things

Philosophers like to present their works as if everything before it was wrong. Sometimes, they even say they have ended the need for more philosophy. So, what happens when somebody realizes they were mistaken?

Sartre and Wittgenstein realize they were mistaken. (Getty Images)
Culture & Religion

Sometimes philosophers are wrong and admitting that you could be wrong is a big part of being a real philosopher. While most philosophers make minor adjustments to their arguments to correct for mistakes, others make large shifts in their thinking. Here, we have four philosophers who went back on what they said earlier in often radical ways. 

Keep reading Show less

Withdrawal symptoms from antidepressants can last over a year, new study finds

We must rethink the "chemical imbalance" theory of mental health.

Bottles of antidepressant pills named (L-R) Wellbutrin, Paxil, Fluoxetine and Lexapro are shown March 23, 2004 photographed in Miami, Florida.

Photo Illustration by Joe Raedle/Getty Images
Surprising Science
  • A new review found that withdrawal symptoms from antidepressants and antipsychotics can last for over a year.
  • Side effects from SSRIs, SNRIs, and antipsychotics last longer than benzodiazepines like Valium or Prozac.
  • The global antidepressant market is expected to reach $28.6 billion this year.
Keep reading Show less

Is there a limit to optimism when it comes to climate change?

Or is doubt a self-fulfilling prophecy?

David McNew/Getty Images
Politics & Current Affairs

'We're doomed': a common refrain in casual conversation about climate change.

Keep reading Show less
Scroll down to load more…