Thirty minutes. That’s how long it takes morning light exposure to reset the biological systems that regulate your mood, energy, and sleep—the same systems that winter darkness quietly dismantles.

A growing body of research suggests that light exposure provides what medication can’t: the environmental signal required to synchronize our circadian rhythms and stimulate energy naturally. Rather than simply changing brain chemistry, light gives the body the physical signal it needs to reset its internal clock and boost energy levels and mood.

The Biological Connection

Light does more than illuminate our surroundings. It resets our circadian rhythms, promotes cellular energy production, and signals the release of mood-regulating neurotransmitters and hormones. When our bodies lack light’s vital input, our mental health pays the price.

Special receptors in the eyes transmit information about environmental light to the suprachiasmatic nucleus in the brain—the “master circadian clock” that regulates hormones that are vital for sleep, mood, and hunger. Sunlight stimulates melatonin and serotonin, increasing their ability to “fire” at the correct times and support mental well-being.

Winter disrupts this system. When melatonin and serotonin function improperly, mood can quickly decline into depression. Studies show circadian rhythms are especially sensitive to light variations during winter months compared with summer months, resulting in shifts in sleep and wake times that negatively affect mood.

The disruptions also extend to energy levels. People suffering from seasonal depression often experience lower energy levels and sluggishness. Research suggests that sunlight—especially its red light waves—can penetrate the body and support mitochondria, the cellular structures responsible for producing energy. The eyes also contain higher levels of mitochondria than other parts of the body, making them especially sensitive to light and able to absorb daylight’s energy-boosting effects. Issues with cellular energy production, known as mitochondrial dysfunction, have been suggested as a key underlying factor in the development of depression.

From Skepticism to Acceptance

Morning light exposure is crucial to our circadian rhythms and related depressive symptoms, Michael Terman, a clinical psychiatry professor, editor-in-chief of the Center for Environmental Therapeutics, and a pioneer of light therapeutics, told The Epoch Times.

Terman recalls when the psychiatric community dismissed light therapy for the treatment of seasonal affective disorder (SAD) when he helped launch the Society for Light Treatment and Biological Rhythms in 1988. Psychiatrists were trained to test antidepressant drugs sequentially until one worked—a process he described as long and expensive, often resulting in only partial mood improvement.

The rapid effect of bright-light exposure has surprised researchers over decades of study, Terman said. Unlike medication, however, light therapy has a clear biological explanation for people whose mood changes with the winter seasons.

“A host of behavioral symptoms appeared before the psychological crash, especially difficulty awakening in the morning, general fatigue, and a taste for carbohydrates that were absent in summer,” Terman noted. “These culminated after a month or more with a lapse into clinical depression, and the whole ensemble of symptoms could lift quickly with bright light therapy—even in less than a week.”

A systematic review and meta-analysis confirmed its effectiveness. One randomized clinical trial reported that morning light therapy was comparable in effectiveness to cognitive behavioral therapy, a standardized treatment for SAD.

Terman has spent four decades studying how light affects depression and biological rhythms, helping establish light therapy as a viable treatment.

In Terman’s 2001 clinical trial, however, results hinged on timing. Morning light therapy for SAD was most effective when administered early in the circadian cycle, achieving 80 percent remission compared with 30 percent to 38 percent for evening or late-morning light.

“The most important thing for SAD sufferers to learn is where their internal circadian rhythm lies,” Terman said. “That will reveal the most effective time to use light therapy.”

Light therapy used at the wrong time may be ineffective. Finding the right time, however, doesn’t require measuring melatonin levels. A 19-item questionnaire can indicate your rhythmic state based on daily activities. Completed after winter symptoms emerge, it provides a recommended start time for bright light therapy.

Daily Strategies for Winter

There are a few ways to practice light exposure during winter to reduce depressive symptoms and support circadian alignment.

Keep Consistent Wake Times

Wake at a consistent time, similar to your summer schedule, to start the day. Increase indoor lighting or open window shades if you don’t yet have a light therapy box. Although tempting, avoiding sleeping in on weekends—it allows your circadian rhythm to drift back toward the winter state you’re trying to avoid.

Get Light Exposure Within 30 Minutes of Waking

Bright light treatment for 30 minutes each morning upon waking has been found to significantly improve depressive symptoms. The current recommendation is to use a 10,000-lux light box that mimics a summer sunrise, Terman said.

Natural morning sunlight also helps align circadian rhythms and improve sleep. Lack of exposure can delay biological timing and disrupt hormone regulation. Terman noted that light on cloudy days may not seem bright, but it is still beneficial.

Aim for 30 Minutes to 1 Hour of Daily Light Exposure

Terman recommends not missing opportunities to be outdoors when the sun is up—whether commuting to work, during breaks, or on weekends. Winter weather does not eliminate the benefits of being outside, as sunlight can pass through clothing and still deliver positive benefits.

A study found that people who self-reported more than one hour per day of outdoor daylight exposure during winter months were less likely to experience depressive symptoms than those with less than one hour of daily exposure.

Establish a Proper Nighttime Routine

Evening habits matter. Terman advises avoiding bright household light for a few hours before bedtime. “This will maximize the therapeutic effect of morning bright light and help normalize your winter sleep cycle,” he noted.

Artificial light exposure at night disrupts your circadian rhythm, affecting hormones such as melatonin and glucocorticoids that regulate sleep and mood. Indoor lighting during winter can be up to 1,000 times brighter than natural outdoor light at night, confusing the body’s internal clocks.

Using softer, warmer lights in the evening—or wearing circadian-friendly glasses that block bright and blue light—signals the body to prepare for sleep. Avoiding screens once you’re ready for bed can be especially helpful.

If winter feels heavy, light therapy offers a simple way to improve mood and energy. Seasonal depression reminds us that the body’s biological systems are missing a vital signal—light—and how intentional choices can help restore it. Choose restoration this winter.