Light exposure during the day linked to a 20% lower risk of depression, new study finds. Here's why.

A young woman is seen in profile, her face in shadow and the back of her head in sunlight.
Avoiding light at night and seeking light during the day may be a simple and effective way to improve mental health. (Getty Images)

For years, scientists have spoken about the mental health benefits of getting enough sunlight during the day and putting away your phone at night. Now, the world's largest study on light exposure and mental health has found a strong link between exposure to light and psychiatric disorders — but the timing of the exposure matters.

The study is getting a lot of attention and underscoring the importance of light exposure's impact on the development of certain mental health issues. Here's what you need to know.

What the study says

The study, which was published in the journal Nature Mental Health, found a link between light exposure during specific times of day and the development of certain mental health issues.

What are the key findings?

For the study, researchers analyzed data from 86,772 participants in the UK Biobank, a long-term health study in the United Kingdom. Each participant was analyzed for their light exposure, along with their sleep habits, level of physical activity and mental health status.

The researchers found that people who were exposed to high amounts of light at night had a 30% increased risk of developing depression, along with a higher risk of psychosis, bipolar disorder, generalized anxiety disorder, PTSD and self-harm.

But people who were exposed to higher amounts of light during the day had a 20% lower risk of depression, along with lowered odds of developing psychosis, bipolar disorder, generalized anxiety disorder, PTSD and self-harm.

"Avoiding light at night and seeking light during the day may be a simple and effective, non-pharmacological means of broadly improving mental health," the researchers concluded.

What experts think

It's important to note that the study didn't find that exposure to light at night causes certain mental health disorders (and vice versa with daytime light) — just that there's a link.

"We do know that psychotic disorders, as with many other psychiatric disorders, cause changes to sleep patterns and circadian rhythms," Dr. Samar McCutcheon, a psychiatrist in the department of psychiatry and behavioral health at the Ohio State University Wexner Medical Center, tells Yahoo Life. "Some studies have found that psychotic symptoms are worse at night, or can cause insomnia, which may increase the likelihood that people would have the lights on during nighttime hours."

But exposure to light at night can mess with your circadian rhythm — that is, the physical, mental and behavioral changes that follow a 24-hour cycle, Hillary Ammon, a clinical psychologist at the Center for Anxiety & Women's Emotional Wellness, tells Yahoo Life. "There seems to be a connection between a shift in a person's natural circadian rhythm and increased mental health issues, including psychosis," she says.

Exposure to light at night, particularly blue light that can be emitted from phones and other screens, can make it harder to get to sleep, Jaime Zuckerman, a clinical psychologist specializing in the treatment of adults with anxiety, mood disorders and relationship difficulties, tells Yahoo Life. In fact, a 2022 meta-analysis of 36 studies on blue light exposure and sleep found that people felt less tired after blue light exposure in 50% of the studies, and 33% of the studies found that people slept less after being exposed to blue light. The data also showed that people who were exposed to blue light were more alert after exposure.

There is a known link between lack of sleep and a higher risk of developing certain mental health disorders, Zuckerman says, making avoiding screens at night and getting to bed at a decent time especially important.

At the same time, Zuckerman points to a link between sunlight exposure and a lowered risk of mental health disorders. "Sunlight increases our serotonin levels, which helps with depression, anxiety and self-harm," she says. "It also helps regulate your sleep and circadian rhythm — and that helps with good mental health."

Why it matters

Experts say the study emphasizes the importance of getting natural sunlight during the day and avoiding screens in the lead-up to bedtime. "The key thing is natural light during the day," Zuckerman says. "A lot of people think, 'I have a lot of light in my office,' but that's not the kind of light you want." Experts recommend taking these little steps to increase your light exposure during the day and decrease blue light exposure at night:

  • Take a short walk outside before work or during lunch.

  • Grab your mail while it's still light out.

  • Walk someplace close that you'd usually drive to.

  • Eat lunch outside during your workday.

  • Sit on a bench outside for five minutes during a workday break.

  • Try to work near a window, or eat breakfast next to a window.

  • Adjust settings on your phone to decrease blue light exposure at night (some even have special nighttime settings).

  • Consider reading before bed instead of looking at your phone or watching TV.

  • If it's hard to get sunlight during the fall and winter, consider using a light box at home, which delivers a therapeutic dose of light that can help improve mood.

"It can be beneficial to be aware of your light habits in general, but particularly with the winter months ahead, during which we have less daylight," Ammon says. While sunlight exposure seems minor, Zuckerman says it's definitely not. "Getting enough light at the right time of day can make a big difference in how you feel," she says.