What Is Light Therapy and How Does It Work?

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young man looking at digital tablet device near light therapy lamp
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Fall or winter may be your favorite season, but the shorter days and reduced sunlight can also bring on a type of depression called seasonal affective disorder (SAD), sometimes referred to as the winter blues. Light therapy is a method of simulating outdoor light to treat or prevent (SAD). It helps reset your ‘biological clock’ (circadian rhythms), which controls sleeping and waking.

It may also be used to help with:

  • Sleep disorders

  • Adjusting to a nighttime work schedule

  • Jet lag

  • Other types of depression

  • Dementia

Lighten the Mood

Light therapy, also known as bright light therapy or phototherapy, is thought to ease depression symptoms by affecting brain chemicals linked to mood and sleep. It can be used alone or as part of a holistic approach to SAD treatment, along with psychotherapy and/or antidepressants.

When using light therapy, you sit or work near a device called a light therapy lamp or box. It may be most effective first thing in the morning, though some may find it helpful to start in the evening. You can work with your doctor to figure out the best time of day, how long, and how often to use light therapy. It may take just a couple of days to up to three weeks for improved symptoms.

Does It Really Work?

According to researchers, there is moderate evidence that light therapy is an effective treatment for seasonal depression. Many people with SAD say they feel better after they use light therapy. This may be because light therapy replaces the lost sunlight exposure and resets the body's internal clock.

What to Look for in Light Therapy Box

When choosing a light therapy lamp or box, look for a high-quality product that is proven to be safe and effective. The light should be brighter than indoor light, but not as bright as direct sunlight. To avoid skin or eye damage, opt for a lamp that emits little to no ultraviolet (UV) light. Also avoid full-spectrum light, heat lamps and tanning lamps or beds, which have not been proven to work for seasonal depression.

Light therapy boxes are labeled according to light intensity, or lux. In general, the light should be 10 to 20 times more intense than standard indoor light. Light therapy boxes typically have bulbs emitting 5,000 to 10,000 lux. The less lux the lamp, the longer the session.

Is Light Therapy Safe?

Light therapy is generally safe and carries little risk. For many people, there are fewer, or more tolerable, side effects with this type of therapy than with antidepressants. If you experience side effects, it may help to adjust your time under the light or move further away from the lamp.

The most common side effects of light therapy include:

Ask your doctor about precautions you should take before trying light therapy. And always tell your doctor if you are using other treatments for depression, or if you plan to discontinue other treatments before starting light therapy.

Use caution if:

  • You have sensitive eyes or skin.

  • You take medications or supplements that increase your sensitivity to sunlight, such as St. John’s Wort, anti-inflammatories or certain antibiotics.

  • You have bipolar disorder. (Light therapy may trigger mania in some people with bipolar disorder.)

If you’re struggling with depression or a case of the winter blues, and you find other treatments aren’t effective, consider light therapy. You and your doctor can work together to find a solution that’s right for you. 

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Medical Reviewer: William C. Lloyd III, MD, FACS
Last Review Date: 2019 Oct 30
THIS TOOL DOES NOT PROVIDE MEDICAL ADVICE. It is intended for informational purposes only. It is not a substitute for professional medical advice, diagnosis or treatment. Never ignore professional medical advice in seeking treatment because of something you have read on the site. If you think you may have a medical emergency, immediately call your doctor or dial 911.
  1. Light Therapy. Mayo Clinic. https://www.mayoclinic.org/tests-procedures/light-therapy/about/pac-20384604
  2. Seasonal Affective Disorder: Bring on the light. Harvard Health Publishing. https://www.health.harvard.edu/blog/seasonal-affective-disorder-bring-on-the-light-201212215663
  3. Light Therapy. University of Michigan Medicine. https://www.uofmhealth.org/health-library/aa111200spec
  4. Light Therapy for Seasonal Depression: Does It Work? https://www.psychologytoday.com/us/blog/evidence-based-living/201612/light-therapy-seasonal-depression-does-it-work
  5. Bright Lights, Big Relief. American Psychological Association. https://www.apa.org/research/action/light