What is light therapy?
Light therapy, also known as phototherapy, is a treatment involving exposure to an artificial light source.
The therapy primarily treats major depressive disorder (MDD) with seasonal patterns (formerly known as seasonal affective disorder, or SAD).
This is a type of depression that occurs during a certain time of year, usually in the wintertime when there’s less daylight. Light can also be used to treat other conditions, including sleep disorders and other types of depression.
How light therapy works to treat depression
The research on light therapy gives a few reasons why it may improve the symptoms of depression. Reasons include that it:
- works on your biological clock by aligning your brain’s 24-hour cycle (aka circadian rhythm)
- balances the activation of serotonin circuitry in your brain, which is a key component in mood regulation
- contributes to stable and consistent sleep patterns
- increases alertness
The extent to which light therapy works for you depends on the light wavelength, duration of use, and your personal circadian rhythm patterns.
Circadian rhythms are cycles of important body functions that happen over a 24-hour cycle and can affect hormones, sleep schedules, and eating habits.
How it works
Light therapy compensates for the lack of exposure to sunlight that may contribute to major depressive disorder with seasonal patterns.
During a session, you sit near a light box or lamp, which emits bright light. The box or lamp usually mimics natural sunlight, but there can be variations between devices made by different manufacturers.
The standard output of a light therapy box is in the range of 2,500–10,000 lux. A lux is a measure of light brightness.
Treatments usually begin in the fall and continue until early spring. The length of the session depends on how well you handle the treatment and the strength of the light box.
Guidelines for typical bright light therapy will usually suggest starting with 10,000 lux for 30 minutes every morning, but someone new to the method may require shorter initial treatments. The more powerful the light box, the shorter the treatment session may be.
Side effects
Some people shouldn’t use light therapy, especially those who:
- have medical conditions that make eyes sensitive to light
- take medications, like some antibiotics or antipsychotics, that increase light sensitivity
If you’re considering this therapy, you should consult a doctor if you have any of the following conditions:
- sensitive skin
- eye conditions
- a history of skin cancer
Some people may also experience euphoria or irritability, which is a sign to stop using the device and speak with a doctor.
For those who can use light therapy, there are still potential side effects. Usually, these can be dealt with by adjusting the duration, intensity, or timing of the sessions.
Side effects may include:
- headaches
- eyestrain
- agitation
- irritability
- problems with sleeping
- fatigue
- blurry vision
You can discuss these side effects with a doctor, but you may also find relief through some simple changes. Avoid using the lamp before bedtime to prevent insomnia, and place the light box further away from you to prevent eyestrain and headaches.
Pros of light therapy
In addition to the possible benefits for improving depression symptoms, light therapy is generally easy to start and adjust according to how it makes you feel.
Light therapy is:
- Accessible. The treatment can be done at home using rented or purchased light boxes.
- Noninvasive. It provides an alternative or add-on to medical interventions like medications, but is not taken internally.
- Safe. Although there are some possible side effects, especially when the lamp is used incorrectly, light therapy is generally safe and low-risk.
- Convenient. You can use a light therapy lamp at home, while you read or eat breakfast. You can also stop light therapy for a few days without adverse effects or the return of symptoms.
- Associated with few or mild side effects. Most of light therapy’s side effects, like headaches, dizziness, or nausea, are preventable by adjusting how you use the lamp.
Light therapy also has potential uses beyond MDD with seasonal patterns, but it’s always important to discuss starting any new therapy with your doctor.
Cons of light therapy
The negative aspects of light therapy are the side effects and complications that can occur. These include:
- headache
- insomnia
- fatigue
- eyestrain
- euphoria
- irritability
Insurance may not cover the cost of a light therapy lamp, even if your doctor prescribes it. This expense can be a barrier for some people.
Achieving results with a light therapy lamp takes time — at least a few days. Getting a benefit from the lamp requires consistent use at the same time every day.
What the research says
Light therapy may be used as a stand-alone or add-on treatment.
While most research has focused on light therapy for treating MDD with seasonal patterns, academic research has started to look into using light therapy for other conditions, including other mood disorders and sleep disorders.
Dr. Carl Vincent, a psychologist in Moline, Illinois, suggests that light therapy be used with other treatments, such as psychotherapy or a drug regimen.
“The idea is that it could be used as a supplemental therapy,” Vincent says. “In addition to treatment, people suffering from depression in the winter months should try to be more active. Winter is a time when people tend to be more sedentary, and getting more exercise can help improve mood.”
A 2016 study involving 122 participants with MDD found light therapy — either alone or in combination with the antidepressant medication fluoxetine (Prozac) — was effective for improving depression symptoms.
A 2017 trial of people with bipolar I or II disorder found light therapy improved depression remission rates and lowered depression rates over a 6-week trial period. The light therapy was an adjunct to bipolar disorder treatment, and the researchers did not observe any changes in mood polarity.
How to do light therapy at home
Before you start light therapy, it’s a good idea to talk with a doctor or mental health professional. Light therapy may interact with other treatments you’re currently taking, such as medications.
Once you’ve had a doctor’s sign off, you can start by reading the instructions provided by the light box manufacturer.
A light with lower intensity may require longer exposure time — meaning you’ll have to sit in front of the box longer. The instructions can also help you identify specific risks and hazards for the brand of the light.
To use a light therapy lamp with 10,000 lux intensity, follow these steps:
- Place the lamp on a counter, desk, or other surface.
- Sit or stand at the correct distance from the lamp according to the manufacturer’s instructions.
- Keep your eyes open and do not sleep during light therapy sessions.
- Do not stare directly at the light box or lamp.
- Start with 30 minutes of exposure per day.
- Schedule light therapy sessions as soon as possible after waking up, between 6:00 a.m. and 9:00 a.m.
You can adjust this schedule and the duration of sessions according to how you feel. You can also try passing the time in front of the light box with an activity like reading a book or working, as long as you’re still facing the light.
How long does it take for light therapy to work for depression?
Many people experience some benefits from light therapy within a few days.
Symptoms of depression should improve in about 2 weeks. If they do not, you can increase your time in front of a 10,000 lux lamp to 60 minutes per day. If this does not work, you can reach out to a doctor for advice.
If you find that light therapy works for you, you may want to make changes to the routine. For example, you can reduce the time in front of the lamp to 15 minutes, or schedule it at a different time of day.
You can also take a break from light therapy for a day or two. However, most people with MDD with seasonal patterns continue to use light therapy regularly over the winter (or days when there’s less sunlight available) to prevent symptoms from returning.
The takeaway
Light therapy may be used to treat major depressive disorder with seasonal patterns, sleep disorders, and other types of depression.
It’s often effective, possibly due to the effects on your circadian rhythm and levels of serotonin in the brain.
Light therapy may have several side effects, but most of these are mild and can be prevented. Talk with a doctor if you feel light therapy might be a good treatment option for you.
Seasonal affective disorder treatment: Choosing a light box
Light therapy boxes can offer an effective treatment for seasonal affective disorder. Features such as light intensity, safety, cost and style are important considerations.
By Mayo Clinic Staff
Seasonal affective disorder (SAD) is a type of depression that typically occurs each year during fall and winter. Use of a light box can offer relief. But for some people, light therapy may be more effective when combined with another SAD treatment, such as an antidepressant or psychotherapy, also called talk therapy.
Light boxes are designed to deliver a therapeutic dose of bright light to treat symptoms of SAD. There are many different types of light boxes. All light boxes for SAD treatment are designed do the same thing, but one may work better for you than another.
Talk with your health care provider first
It’s best to talk with your health care provider about choosing and using a light box. If you’re experiencing both SAD and bipolar disorder, the advisability and timing of using a light box should be carefully reviewed with your health care provider. Increasing exposure too fast or using the light box for too long each time may induce manic symptoms if you have bipolar disorder.
If you have past or current eye problems such as glaucoma, cataracts or eye damage from diabetes, get advice from your eye specialist before starting light therapy.
Understanding a light box
A light therapy box mimics outdoor light. It’s thought that this type of light may cause a chemical change in the brain that lifts your mood and eases other symptoms of SAD, such as being tired most of the time and sleeping too much.
Generally, the light box should:
- Provide an exposure to 10,000 lux of light
- Produce as little UV light as possible
Typical recommendations include using the light box:
- Within the first hour of waking up in the morning
- For about 20 to 30 minutes
- About 16 to 24 inches (41 to 61 centimeters) from your face, but follow the manufacturer’s instructions about distance
- With eyes open, but not looking directly at the light
Light boxes aren’t regulated by the Food and Drug Administration (FDA) for SAD treatment, so it’s important to understand your options.
You can buy a light box without a prescription, but it’s best to use it under the guidance of a health care provider and follow the manufacturer’s guidelines. Your health care provider may recommend a specific light box. Most health insurance plans don’t cover the cost.
What to consider
Here are some questions to think about when buying a light box for seasonal affective disorder:
- Is it made specifically to treat SAD? If not, it may not help your depression. Some light therapy lamps are designed for skin disorders — not for SAD. Lamps used for skin disorders mainly produce ultraviolet (UV) light and could damage your eyes if used incorrectly.
- How bright is it? Light boxes produce different intensities of light. Brighter boxes will require less time to use each day, compared with dimmer boxes, to achieve the same effect. Usually, the recommended intensity of light is 10,000 lux.
- How much UV light does it release? Light boxes for SAD should be designed to filter out most or all UV light. Contact the manufacturer for safety information if you have questions.
- Can it cause eye damage? Some light boxes include features designed to protect the eyes. Make sure the light box filters out most or all UV light to avoid damaging your eyes. Ask your eye specialist for advice on choosing a light box if you have eye problems such as glaucoma, cataracts or eye damage from diabetes.
- Is it the style you need? Light boxes come in different shapes and sizes, with varied features. Some look like upright lamps, while others are small and rectangular. Smaller light boxes are more portable and easier to pack if you’re traveling during fall and winter. The effectiveness of a light box depends on daily use, so buy one that’s convenient for you.
- Can you put it in the right location? Think about where you’ll want to place your light box and what you might do during its use, such as reading, doing a craft or watching TV. Check the manufacturer’s instructions, so you receive the right amount of light at the proper distance.
Talk to your health care provider about light box options and recommendations, so you get one that’s best suited to your needs.
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- AskMayoExpert. Seasonal affective disorder (SAD). Mayo Clinic; 2021.
- Seasonal affective disorder. National Institute of Mental Health. https://www.nimh.nih.gov/health/publications/seasonal-affective-disorder/. Accessed Dec. 21, 2021.
- Bais B, et al. Light therapy for mood disorders. In: Handbook of Clinical Neurology, Vol. 182. Elsevier; 2021. doi:10.1016/B978-0-12-819973-2.00004-6. Accessed Dec. 22, 2021.
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- Seasonal affective disorder and complementary health approaches: What the science says. National Center for Complementary and Integrative Health. https://www.nccih.nih.gov/health/providers/digest/seasonal-affective-disorder-and-complementary-health-approaches-science. Accessed Dec. 21, 2021.
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