Scientists Shed Light on Different Uses of Light Exposure Therapy

Editor’s note: [The intention of this article is to introduce the reader to seasonal affective disorder and light exposure therapy. It is in no way a replacement to medical advice. If you would like more information about the disorder and its treatment contact a medical professional in your area. If you have medical questions, please contact your health care professional.]

Although we sometimes romanticize winter as a season of sparkling white snow to play in, it’s common for people to feel a little down during the first months of the year. Winter’s characterized by short days with little sunlight and troublesome weather, after all. But winter makes some people feel more than a little blue; they feel downright miserable.

Some people are depressed enough to be diagnosed with seasonal affective disorder, but there is treatment known as light exposure therapy.

What is Seasonal Affective Disorder?

According to professor Scott Lilienfeld and other authors of the textbook “From Inquiry to Understanding,” seasonal affective disorder, or SAD, can be defined as “depressive episodes that display a seasonal pattern, most commonly beginning in fall or winter and improving in spring.”

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Exposure to the sun usually accounts for these rises and falls in mood. The psychologists go on to note that “there must be two consecutive years in which the episode appears on a seasonal basis” to make a diagnosis. “Symptoms often include weight gain, lack of energy, carbohydrate craving, and excessive sleep,” they added.

SAD plagues millions of people. In 1989, psychiatrist N. E. Rosenthal estimated that roughly 6.1 percent of Americans, which is about 10.8 million people, suffer from SAD. The percentage today might be even higher since we’re becoming more dependent on technology for work and entertainment. Many people with SAD are women living far from the equator, the middle latitude of Earth where the sun hits most directly, according to psychologist David G. Myers.

The Basics of Light Exposure Therapy

Myers reported that the idea of light exposure therapy arose in the early 1980s, when the National Institute of Mental Health made a connection that might seem obvious now. Since winter has little sunlight, perhaps SAD patients would benefit from artificial sunlight.

In an experiment, 61 percent of SAD patients exposed to artificial morning light saw their spirits lifting after just four weeks. Only 32 percent of the control group exposed to a dim light placebo improved. This treatment has become known as light exposure therapy, phototherapy, or simply light therapy.

Myers noted that, since then, they’ve found that 30 minutes of light exposure therapy a day usually treats SAD symptoms just as well as antidepressant drugs or cognitive-behavior therapy. This is especially valuable news for pregnant women or other people who can’t take many medications. And numerous patients see improvement after just a few days or a couple weeks if the dosage is right, which is incredible compared to most psychological treatments.

For light exposure therapy to work, a person needs to do more than sit next to a light bulb. Products often known as “light boxes” are designed to give off intense light, usually 10,000 lux of white fluorescent light. To put that in perspective, the average living room in Australia was lit by 50 lux in 1998, according to Alan Pears, an environmental consultant.

The Mayo Clinic warns that, like most psychological care, light therapy does not cure SAD by getting rid of it, but rather treats it by diminishing the symptoms. Thus, it is important to maintain a consistent schedule of light exposure even after the person feels happier and more energetic. Also, the therapy is often used in conjunction with other treatments such as counseling and antidepressants rather than as a means of replacing them entirely.

Using a Light Box

The Mayo Clinic went on to note that light therapy is the safest and most effective when the patient follows a detailed set of guidelines. Although most light boxes come with their own instructions, the general principles guiding their usage are the same.


-depression-Scientists Shed Light on Different Uses of Light Exposure Therapy


The person with SAD must allow the light to enter their eyes indirectly. Their eyes must be open, and the light should bathe their face—but looking directly into a 10,000-lux light isn’t much brighter than looking directly into the sun. Rather than just sit there, the user can read, use a computer, apply makeup, and more as the light shines.

This treatment usually lasts 30 minutes, though some people have to work their way up to dosages of two hours. Doing too much right away may affect a person’s sleep or make them jittery.

Most medical experts and light box manufacturers recommend using it shortly after getting out of bed to help the individual become fully awake. According to a study by Katarzyna Baczynska, “prolonged exposures to light in the evening and at night can delay melatonin production, sleep onset, [and] reduce subsequent sleep quality.”

However, according to the light box manufacturer Nature Bright, light exposure therapy in the evening might be helpful for people who fall asleep too early most nights. People working the “graveyard shift” can come up with their own exposure schedules as well.

Types of Light Boxes

Once a person knows how they’ll use a light box, it’s time to pick one out. According to the Mayo Clinic, health insurance rarely covers the cost of light exposure therapy. However, there are plenty of effective light boxes available on general websites like Amazon or specialized medical websites for $50 to $100, though larger light boxes might cost more. Cheaper ones might be too small or prone to defects.

Although most light boxes give off 10,000 lux of light, others aren’t as bright or make this amount adjustable. A dimmer box means longer treatment time, according to Baczynska. More importantly, it’s essential to make sure the box is advertised as flicker-free, since flickering light can be harmful to the eyes, especially when it’s in a person’s peripheral vision.

A small light box might sound convenient, but it allows for little movement.Credit:

-depression-Scientists Shed Light on Different Uses of Light Exposure Therapy

A small light box might sound convenient, but it allows for little movement.Credit:’s John Cline, also warns that no legitimate light boxes use incandescent lamps since they put out dangerous amounts of infrared illumination. Also, the prospective light box should be free of UV rays, which can harm a person’s skin.

Aside from those precautions, practical concerns apply as well. In terms of physical size, a small light box might be more convenient, but it must be aimed at the user’s face perfectly, so they cannot move around much at all. How it stands and whether or not its aim can be adjusted are other factors to consider.

According to Dr. Jim Phelps, some studies suggest the light works better if it is above the user pointing down at them because this more closely simulates the sun in the sky. In addition to these crucial differences, many light boxes have helpful features such as a timer for the user’s own convenience.

Although picking a light box may sound stressful, it should be a valuable tool after finding the right one. It can be used almost anywhere, whether at home or at work. Plus, it’s especially suitable for people who have to arrive at work or school too early to receive much sunlight.

Side Effects

Part of the reason why light exposure therapy is so appealing is the fact that its side effects are often mild and rare, in strong contrast to most antidepressant drugs. But a person using a light box should watch out for headaches, irritability, and nausea, as Yevgeny Botanov and Dr. Stephen S. Ilardi have found.

While some have complained about eyestrain, Botanov and Ilardi noted that research participants exposed to the placebo of a dimmer light have the same concern just as often as actual patients, so they might just be imagining the effect out of concern for their eyesight.

Arcady A. Putilov, and Dr. Konstantin V. Danilenko, pointed out that no study has been done to see how long it takes for light exposure withdrawal effects to kick in, so it’s important to make time for it every day. Mayo Clinic also warns that exposure to such bright light should be limited for people who have sensitive skin, especially due to a medication. Notably, St. John’s Wort, a supplement often used to treat different forms of depression including SAD, makes people especially sensitive to sunlight.

How the Therapy Works

So, how does sitting next to a bright light for about 30 minutes a day make a person with SAD happier and more energetic? Well, it’s important to note that humans weren’t designed to spend most of our lives indoors, but cultural shifts in how we work and how we find entertainment are keeping us in buildings most of the day. Our race has yet to adapt to this change, so an increasing number of people are experiencing health problems because of it.

In terms of SAD, it’s most important to note that indoor lifestyles often prevent people from getting all the sunlight they need. This is especially problematic during the winter months when the sky is often cloudy and dark. Even exposure to sunlight through windows becomes more difficult to find.

During other seasons, a person with SAD might find their symptoms acting up during long periods of dark weather, as the Mayo Clinic noted. It’s no surprise, then, that people living far from the equator are most likely to have SAD.

When a light box uses its intensely-powerful light to simulate the sun, it has a direct impact on the mind. According to Myers, brain scans show how the therapy affects regions that influence the body’s arousal and hormones. The most likely candidate behind these improvements is the change in melatonin production.

Melatonin, secreted by the brain’s pineal gland, is produced mostly at night to help people sleep. It’s the main chemical behind circadian rhythm, the sleep-wake cycle. In one study, psychologists noted that “many patients with SAD have phase-delayed circadian rhythms,” which means that their bizarre melatonin production peaks too late at night and takes too long to taper off during the day. People with SAD often feel tired, unmotivated, and downright depressed in part because their melatonin is telling them to do nothing during the day.

Naturally speaking, the sun tells the human body when it’s time to wake up, and that slows down melatonin production. So, light exposure therapy is simply an artificial way of waking up a person’s body and telling their melatonin production to slow down for the day ahead. And since melatonin production now stops at the correct time, it will eventually start at the right time as well. Basically, the SAD patient will feel fully awake after their light exposure in the morning, and then they’ll feel fully tired by night. Cline noted that a patient’s improvement in sleep timing often reflects their improvement in SAD symptoms overall.

Many light box users eat breakfast during their therapy.Credit:

-depression-Scientists Shed Light on Different Uses of Light Exposure Therapy

Many light box users eat breakfast during their therapy.Credit:

But there’s more to the lift in mood than just feeling less tired. Specifically, the Mayo Clinic notes that excessive and irregular melatonin output is also linked to depression. Which other chemicals come into play might be found with further study. After all, light exposure therapy only began in the 1980s, so many more studies need to be conducted to unearth its intricacies.

Putilov and Danilenko noted that an alternative to light boxes is to simply get outside in the morning if the sun’s out. After all, hour-long walks in the sunshine have shown perfectly fine remission rates for patients with SAD.

The psychologists also warn that light boxes may only help patients due to the placebo effect. That is, a light box may boost a patient’s mood mostly because they believe it will, not because the treatment itself has major effects. Specifically, some clinical trials have shown that patient expectations play an important role in how well the therapy works.

It’s also problematic that the nature of light exposure therapy doesn’t make a double-blind study easy to perform. In many tests, the control group is exposed to a dim red light, and the researchers tell the participants this will boost their mood. However, patients with the actual bright lights tend to have greater expectations for their exposure than the ones with a dim light. Making experimental conditions that rule out the possibility of the placebo effect is an important challenge facing light therapy researchers today.

Treatment of Other Conditions

Research on how light exposure therapy can treat ailments other than SAD is starting to come to light, though. Unsurprisingly, it can treat a variety of sleep disorders. But early studies suggest that it can also help people with non-seasonal depression, Parkinson’s disease, Alzheimer’s, menstrual-associated disorders, and bipolar disorder.

In one study, researchers found that light exposure can help subsyndromal seasonal affective disorder, or SSAD. “SSAD patients experience symptoms such as low mood, low energy, increased sleep, increased appetite, weight gain and decreased social activity” during certain seasons, as the researchers noted. However, unlike full-blown SAD patients, they “do not fulfill criteria for major depression” such as extreme anxiety, loss of pleasure, or a sense of meaninglessness. If the timing of the research participant’s symptoms were closely aligned to the seasons, then they were more likely to see improvement with light exposure therapy.

But the treatment can also help people with depression that doesn’t follow a seasonal pattern. According to Putilov and Danilenko, some people with depression exhibit symptoms common in SAD as well, such as sleeping too much, overeating, craving carbohydrates, and being lethargic. Depressed people with these symptoms are likely to benefit from light exposure therapy. However, those with insomnia, early morning wakening, poor appetite, and agitation are less likely to see improvement.

Surprisingly enough, one study suggests that light therapy might even help with the treatment of Parkinson’s disease, which often comes packaged with insomnia and depression. Dopamine replacement therapy and antidepressants can cause poor side effects, so light exposure therapy may be a huge relief for some.

Gregory L. Willis and E. J. D. Turner took a small sample of 12 patients and had them undergo the therapy every evening since their circadian rhythms were phase-advanced, producing too much melatonin too early in the night. This is common in Parkinson’s disease patients since dopamine injection treatment can raise melatonin levels too high.

The team saw improvement in their subjects after just two weeks of treatment. The symptoms of bradykinaesia (slowness in movement), rigidity, agitation, dyskinesia (impairment of muscle control), and psychiatric side effects reduced. The participants also slept better, felt happier, and had higher appetites and libidos. Many of the patients had their daily doses of dopamine safely lowered thanks to the bright-light treatment, which helped cut back on problematic side effects. This successful treatment deserves further investigation in other research studies with larger sample sizes.

Light therapy can also help Alzheimer’s patients stay active. Glenna A. Dowling, and her team used strong artificial light on a sample of patients every morning to decrease their melatonin production. Then, in the evening, they gave the patients a melatonin supplement to spur it along once again. An improved sleep-wake cycle allowed Alzheimer’s patients to stay awake longer and perform more activities throughout the day. However, the melatonin supplement was a necessary part of the treatment: light exposure alone saw little effect.

Additionally, women with menstrual-associated disorders might benefit from light exposure therapy. Mary Lee Barron, a professor of nursing at Saint Louis University, has examined the physiology surrounding light exposure, menstrual cycles, and melatonin secretion. More research needs to be performed, but it’s clear that these women are sensitive to changes in light and dark, meaning that a balanced exposure of each can help keep melatonin secretion at proper levels.

Dr. Dorothy Sit and her team also found in a study that midday exposure to light can help female bipolar patients reach a “euthymic mood,” that is, a normal mood that’s neither depressed nor manic. However, the team warns that “women with bipolar illness are highly sensitive to morning bright light treatment,” so it should be introduced slowly, starting at only 15 minutes a day. It should not be used on days of hypomania.

Research on how light exposure therapy can treat conditions other than SAD is still incredibly young. With the limited number of studies available, it’s too early to say it is effective for all these disorders. However, given the low cost of a light box and the small risk of side effects, it might be worth a try if you suffer from one of these conditions. At the very least, you can hope for better sleep. And if you think your case of the “winter blues” is oddly severe, then it may be time to consult y

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