Light therapy, also known as phototherapy, is a treatment in which the patient is exposed to an artificial light source. The therapy primarily treats seasonal affective disorder (SAD). Seasonal affective disorder is the formal name of a type of depression that occurs during a certain time of year, usually winter. Light is also used to treat other conditions, including sleep disorders and other types of depression.

How It Works

Typically, light therapy is meant to compensate for the lack of exposure to sunlight that is thought to be linked to SAD. The patient sits near a machine called a light box, which emits strong light. The light usually mimics natural sunlight though there are variations. A unit of measure called a lux gauges the amount of light used in a treatment. The standard output of a light box is between 2,500 and 10,000 lux.

Treatments usually begin in the fall and continue until early spring. Sessions commonly last from 10 to 15 minutes. The length of the session depends on how well a patient can handle the treatment and the strength of the light box. Someone new to the method may be given shorter initial treatments. The more powerful the light box, the shorter the treatment session can be.

Although light therapy has been shown to be effective, why it is effective is still being studied. One theory is that light naturally triggers serotonin (the “feel good” brain chemical) production in the brain. Some experts believe that success with light therapy is due to a placebo effect.

There are side effects to light therapy, including headache and sunburn, but they are generally not serious. Most can be dealt with by adjusting the duration and intensity of the sessions. Eye drops, nasal drops, and sunscreen can also alleviate some symptoms.

People with sensitive skin, eye conditions, or a history of skin cancer should consult a physician if considering this therapy. 

Pros of Light Therapy

Light therapy has many positive aspects. Light therapy is:

  • noninvasive
  • safe
  • convenient (light boxes can be rented or purchased for home treatment)
  • generally has few or mild side effects

Cons of Light Therapy

The negative aspects of light therapy are the side effects and complications that could occur. These include:

  • headache
  • insomnia
  • sunburn
  • fatigue
  • dry eyes and nose
  • hypomania, an extended period of heightened mood

What the Expert Says

Dr. Carl Vincent, a psychologist in Moline, Ill., suggests that light therapy be used with other therapy treatments, such as psychotherapy and/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.”