Suicide rates rise in the spring. Here’s what you need to know.

The erroneous claim often resurfaces around Thanksgiving and lasts through Christmas: Suicide rates go up around the holidays. Maybe it comes from the back-from-the-brink movie classic It’s A Wonderful Life, or the idea that cold, short days dampen people’s moods.

But decades of research has shown the claim to be false. Suicide rates do not increase over the holidays.

The danger zone is actually right about now, when the days get longer and the flowers start to bloom. That’s when there’s a slight increase in deaths by suicide.

Data from the U.S. Centers for Disease Control and Prevention show that suicide rates across the U.S. tend to reach their highest point each year sometime between March and August. In 2016 — the most recent year for which data are available — the months with the highest average daily suicides were August and July. The previous year it was May, July, and March.

The trend has been shown across the globe, with suicide rates in South Africa rising in September and October, the southern hemisphere’s spring.

“It does sound counterintuitive,” said Dan Romer, research director of the Annenberg Public Policy Center at the University of Pennsylvania. “You’d think it would be higher when it’s dark and gloomy ... but the increase in the spring is very reliable. You can see it every year.”

That’s not to say there’s a sudden, large jump, Romer said. It’s a modest increase.

In 2016, the month with the lowest suicide rate (December) had an average of 110 daily suicide deaths across the nation, versus the month with the highest rate (August), which had an average of 130 daily suicide deaths.

Suicide is a public-health concern all times of the year, Romer said, and with overall suicide rates increasing in the last few decades, people should always be on the lookout for signs of concern. Those include people talking about wanting to die, feeling trapped or in unbearable pain, or being a burden to others. (See a list of suicide warning signs here.)

If you notice these signs in someone you know, ask the person directly about suicidal feelings, Romer said. You can also call the National Suicide Prevention Lifeline at 1-800-273-8255 or text TALK to the Crisis Text Line at 741741.

While researchers have been tracking the trend of suicides rising in the spring for decades now, they still know very little about what causes it.

“The most prudent conclusion is that we don’t understand it,” said Maria Oquendo, chairman of the department of psychiatry at the University of Pennsylvania's Perelman School of Medicine.

But that doesn’t mean there aren’t interesting theories out there.

One blames a common springtime nuisance: pollen.

Pollen is well-known for causing inflammation in the throat, nose, and eyes — what millions of Americans experience as allergies. But many tissues in the body respond to allergens, Oquendo said, including the brain.

Inflammation in the brain has been linked to mood disorders, with studies showing patients on medications that increase inflammation (such as those given for Hepatitis C) are more likely to develop depression and suicidal thoughts even without a prior history of mental illness.

“It’s still circumstantial evidence,” Oquendo said, adding that it does make this an interesting idea to research further.

Another theory is that when there is more daylight, people have more energy.

That may seem to be more reason to be happy, but “you also need a certain amount of energy to end your life,” Romer said.

Most people who die by suicide have thought about it before, but they may not have chosen a method or made a plan to act on that thought.

“There’s an activation component with daylight,” Romer said.

Oquendo said that this theory is widely espoused by psychiatrists, but that there is little research to prove it.

Some mental-health professionals also suggest that there could be a social component to it. As spring rolls around with more sunshine and warmer weather, there’s an expectation for people to be more social — to see friends at picnics or parties, explore the outdoors together.

If people don’t have that experience, it can exacerbate feelings of loneliness and disappointment.

“But that’s exactly what people said about the holidays and it turned out that wasn’t the case,” Oquendo said. That doesn’t mean it can be ruled out, but people should be skeptical of that theory, she said.

For teenagers — an age group in which suicide is the second leading cause of death — the seasonal trends have more to do with school than weather or daylight, said Tami Benton, psychiatrist-in-chief at Children’s Hospital of Philadelphia.

“Spring is the time when students start having an idea of how the school year is going to end,” she said. “If it hasn’t gone well and students have poor grades or will have to repeat a grade, that’s when we see kids having more problems.”

Spring is also when high school seniors hear back from colleges they’ve applied to and have to make a decision about which they’ll attend. Those types of stressful situations can worsen symptoms for kids dealing with depression, anxiety, and other mental illness.

Benton said the hospital typically sees an increase of kids in the emergency room for mental-health concerns in both the fall, when school begins, and the spring.

Parents and teachers may want to monitor kids more closely during those times, she said. Changes such as increased irritability, isolation, or impulsivity might signal a need for a deeper conversation.

But for the general population, Oquendo said, there’s little reason to recommend different public-health measures in the spring. “People should be vigilant about suicide risk all the time,” she said.

If you or someone you know is in crisis, call the National Suicide Prevention Lifeline at 1-800-273-8255 or text TALK to the Crisis Text Line at 741741.