As the days grow colder and daylight becomes more scarce, some Americans are oversleeping, overeating, experiencing weight gain and social withdrawal or hibernating.
The symptoms are part of a condition called seasonal affective disorder, also known as SAD or seasonal depression.
The National Institute of Mental Health defines seasonal depression as periods where people feel sad or not like their usual selves, typically when the seasons change.
Some people feel down when the days get shorter in the fall and winter, also called the winter blues, and start to feel better in the spring when there are longer daylight hours.
These symptoms can lead to what medical professionals call a clinical level of depression, where feelings of sadness and other symptoms impact daily activities, said Kristie Norwood, a licensed clinical psychologist and director of Hampton University's Student Counseling Center.
Summertime and depression: Seasonal depression isn't just for winter. Summer can trigger a mood disorder too.
How many people are impacted by seasonal depression?
Nationally, seasonal depression affects 5% of the total population – its impact isn't as wide as other psychological conditions, but the condition still exists, Norwood said.
Dr. Ankit Jain is a psychiatrist at the Milton S. Hershey Medical Center in the Penn State Health system. He said in most cases, seasonal depression symptoms start in the late fall or early winter and go away during the summer or spring months.
However, of those who have seasonal depression, 10% can have it in summer too, Jain said.
What causes seasonal depression?
Christopher Hagan, a licensed clinical psychologist and assistant professor at Cornell College in Iowa, said medical professionals still don't fully understand exactly what causes seasonal depression. They do know, however, that a lack of daylight is part of it.
"If we're doing less of the things that we enjoy, seeing people less often, spending less time outside, getting less exercise or less activity, all of those things are going to contribute to depression for some people," Hagan told USA TODAY.
Seasonal depression symptoms include agitation, weight gain and more
According to Jain and the Mayo Clinic, symptoms of fall and winter seasonal depression include:
Appetite changes, especially a craving for foods high in carbohydrates
Tiredness or low energy
For those suffering from seasonal depression during the spring or summer, symptoms include:
Trouble sleeping (insomnia)
Agitation or anxiety
Does daylight saving time impact mental health?
Norwood, from Hampton University, said once daylight saving hits, a signal is sent to our brains that "something's happening."
People who live on the East Coast and are used to having a significant amount of daylight may have trouble with these changes. We think we should be asleep or resting, when really, we're supposed to be up and active despite it being dark outside.
Jain, from Pennsylvania, also said daylight saving time significantly impacts people's health.
The transition in and out of daylight saving time can cause sleep disruption, which can lead to mood disturbances, especially among people who are already diagnosed with anxiety or depression, he said.
"When the time changes ... the brain is already struggling with the balance of serotonin and melatonin levels," he said. "Due to less sunlight during the winter time, the struggle is furthered by daylight saving. Our bodies really struggle to adjust to the new light and new timeframe."
Jain also referred to a 2017 study from Denmark that found the transition from summer to standard time was associated with an 11% increase in depressive episodes; the episodes stopped over 10 weeks, the researchers found.
Is daylight saving time healthy for you? No, experts say, pointing to lost sleep
Changing clocks: How to cope with the impact of a time change
How does light therapy help people suffering from seasonal depression?
One common treatment for seasonal depression is light therapy, which has been used to treat seasonal depression for nearly 40 years, Jain said.
During light therapy, people are exposed to a light every day during the winter months to make up for the "diminished natural sunlight in the darker months," he said.
Patients sit in front of a bright light box that gives off 10,000 lux, which is a unit of illuminance. Typically, people sit in front of the boxes every day for about 30 to 45 minutes first thing in the morning.
"These bright light boxes are about 20 times brighter than usual indoor light," he said. "Make sure when you're buying these kinds of boxes, there are UV filters in them because UV can damage the skin (and) predispose you to skin cancer."
Norwood, from Hampton University, cautions that people consult a doctor before undergoing light therapy. There are common mistakes people make that could lead to health issues, she said.
"You don't want to use tanning lamps," said Norwood. "You don't want to stare directly into the light. It should be positioned downward to kind of minimize the glare ... And then doing it for a time period and also building up to it because you don't want to shock your system."
And light therapy isn't the only solution to lessening the symptoms of seasonal depression. It's also vital to be active and engage with more people white undergoing light therapy, Norwood said.
Medications are also known to improve seasonal affective disorder symptoms, including Bupropion, said Jain.
Can tanning beds help people with seasonal depression?
While it hasn't been proven to help people with seasonal depression, some people seem to think tanning beds can be used to combat it.
Medical experts say that's not the case and the risks are far greater than the benefits of using tanning beds to treat seasonal depression.
Jain has had some patients ask about tanning beds as treatment for SAD. Multiple studies have been done on the topic and one in particular found that 80% of people who were using indoor tanners still reported symptoms of seasonal affective disorder.
Some people even reported using ultraviolet-emitting tanning beds to alleviate the symptoms, which can increase the risk for skin cancer, he said.
"The bottom line is no," Jain said. "Tanning beds are not useful and not an effective treatment of seasonal affective disorder."
Hagan, from Cornell College, said it's vital to remember seasonal depression is treatable, and if light therapy isn't for you, cognitive behavioral therapy can help.
"If you know this clearly happens every winter, you can go to treatment, go to therapy, and keep using those skills every year without necessarily having to go back to therapy every year," he said.
If things get particularly bad, returning to therapy is an option too.
"It's a way to learn those skills and kind of prevent it or minimize the impact of it in the future," he said.
Saleen Martin is a reporter on USA TODAY's NOW team. She is from Norfolk, Virginia – the 757 – and loves all things horror, witches, Christmas, and food. Follow her on Twitter at @Saleen_Martin or email her at firstname.lastname@example.org.
This article originally appeared on USA TODAY: Seasonal depression: How many people have it? Symptoms, how to combat