Seasonal affective disorder: Treatment with light therapy

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Seasonal affective disorder: Treatment with light therapy

Seasonal affective disorder — Explore light therapy as a treatment for this type of depression.

In the dark days of fall and winter, you may turn your face to the afternoon sun, seeking out what little light filters through fading gray skies. You may throw open the blinds, leave lights on throughout your home or even head south for a vacation — anything for a little more light. Or you may even be unable to crawl out of bed in the morning.

For people with a type of depression called seasonal affective disorder (SAD), this need for light takes on greater significance. Treatment with light therapy may offer a chance to regain the happier mood and brighter outlook that you lose to seasonal affective disorder. Learn how light therapy works and understand its pros and cons.

Understanding light therapy

In light therapy, you sit with your eyes open in front of a light box — a small, portable device that contains fluorescent bulbs or tubes. The light box emits a type and intensity of light that isn't found in normal household lighting, so simply sitting in front of a lamp in your living room won't relieve the symptoms of seasonal affective disorder. Light therapy mimics outdoor light and causes a biochemical change in your brain that lifts your mood, relieving symptoms of seasonal affective disorder.

Light therapy, also called bright light therapy or phototherapy, has been used to treat seasonal affective disorder since the early 1980s. Many mental health professionals now consider light therapy to be standard treatment for seasonal affective disorder.

However, light therapy hasn't been officially approved as a treatment by the Food and Drug Administration because of a lack of definitive evidence about its effectiveness in clinical trials. Results of some clinical trials have shown light therapy to be effective — and in some cases even more effective than antidepressants — while other research has shown that it's not effective. In addition, most studies have lasted less than six weeks.

You can purchase a light therapy box over-the-counter, which means you don't need a prescription. However, check with your doctor before trying light therapy to make sure it's appropriate for your situation.

Light therapy

Image showing woman undergoing light therapy for seasonal affective disorder

Light therapy is often an effective treatment for seasonal affective disorder. You can sometimes engage in routine activities, such as reading, while undergoing light therapy.

The link between light and seasonal affective disorder

The precise cause of seasonal affective disorder isn't known, but genetics and your age may be factors. Most evidence, though, suggests that it arises from abnormalities in how your body manages its internal (circadian) biological rhythms or matches those rhythms to the 24-hour day. In particular, the hormone melatonin is thought to play a major role in seasonal affective disorder. Melatonin helps control body temperature, hormone secretion and sleep. It's produced in a specific area of your brain during the hours of darkness.

During the low-light months of fall and winter, people with seasonal affective disorder produce more melatonin than normal — enough to cause potentially debilitating symptoms of depression. But exposure to bright light, such as that from a light box, can suppress the brain's production of melatonin, helping regulate your body's internal clock and reducing symptoms.

The benefits of light therapy

Light therapy offers many potential benefits for people with seasonal affective disorder. It may be helpful for you if:

  • You don't want to take medications such as antidepressants
  • You can't tolerate the side effects of antidepressants
  • You've tried antidepressants but they haven't been effective
  • You want an alternative to psychotherapy
  • You're pregnant and concerned about the effects of antidepressants on your developing fetus
  • You lack insurance coverage for mental health services

Treating other disorders
Light therapy may be helpful in treating conditions other than seasonal affective disorder. However, it shouldn't be a substitute for standard treatment. And keep in mind that little research has been done using light therapy for other disorders. These other disorders may include:

  • Depression other than seasonal affective disorder
  • Obsessive-compulsive disorder
  • Premenstrual dysphoric disorder
  • Postpartum depression
  • Some forms of insomnia

Drawbacks and side effects of light therapy

Light therapy isn't for everyone, nor is it always completely effective in reducing all of your symptoms.

Light therapy may trigger episodes of mania in people with bipolar disorder. In addition, although rare, some people, particularly those with severe forms of depression, have reported thoughts of suicide after treatment with light therapy. Light therapy alone may not be fully effective. You still may need treatment with medications or psychotherapy.

Side effects
Side effects from light therapy are uncommon but can happen. They include:

  • Eyestrain
  • Headache
  • Agitation
  • Nausea
  • Insomnia
  • Irritability
  • Fatigue
  • Dry mouth
  • Sleep disruptions

You may be able to manage these problems by reducing treatment time, moving farther from the light box, taking breaks during long sessions or changing the time of day you use light therapy. Talk to your doctor for additional help and advice.

Who shouldn't use light therapy
Don't use light therapy without consulting your doctor first if:

  • Your skin is sensitive to light
  • You take medications that react with sunlight, such as certain antibiotics or anti-inflammatories
  • You have an eye condition that makes your eyes vulnerable to light damage

How to use light therapy

Although you can buy light therapy boxes over-the-counter, it's important to consult your doctor when you use one. Done improperly, light therapy won't be effective, and it could even be harmful.

Averting your eyes
In order for light therapy to work, the light from the light box must enter your eyes indirectly. You can't get the same effect by exposing your skin to the light. But don't look directly at the light box because the light can damage your eyes. The bulbs in the light box are covered with a plastic screen that helps block out potentially harmful ultraviolet (UV) rays that can cause cataracts and skin problems.

Three key elements
Light therapy is most effective when you have the proper combination of intensity, duration and timing:

  • Intensity. The intensity of the light box is recorded in lux, which is a measure of the amount of light you receive at a specific distance from a light source. Light boxes for light therapy usually produce between 2,500 lux and 10,000 lux, with 10,000 lux being typical. In contrast, the lighting in an average living room in the evening is less than 400 lux, while a bright sunny day may register 100,000 lux. The intensity of your light box may also determine how far you sit from it and the length of time you need to use it. The 10,000 lux light boxes usually require only 30 minutes per session, while the 2,500 lux light boxes may require up to two hours per session.
  • Duration. Light therapy typically involves daily sessions ranging from 30 minutes to two hours. When you first start light therapy, your doctor may recommend treatment for shorter blocks of time, such as 15 minutes. You gradually working up to longer periods.
  • Timing. For most people, light therapy is most effective if used in the morning, after you first wake up, rather than during the evening. Doing light therapy at night can disrupt your sleep.

Finding time
Light therapy requires time and consistency. Some people quit because they don't want to spend a lot of time sitting by a light box. But light therapy doesn't have to be boring. You can set your light box on a table or desk in your home or in your office. You can read, use a computer, write, watch television, talk on the phone or eat while undergoing light therapy. Some light boxes are even available as visors that you can wear. Because light therapy seems to work best in the early morning, you may need to wake up earlier than you normally would to match treatment with biological rhythms. You may find that difficult to do, especially if depression leaves you feeling lethargic. Your doctor can help you find a schedule that works for you.

What to expect from light therapy

The general recommendation for most people with seasonal affective disorder is to begin treatment with light therapy in the early fall, as soon as the earliest symptoms start. Be on the alert for such symptoms as difficulty waking, daytime sleepiness and carbohydrate cravings. Treatment generally continues until spring, when outdoor light alone is sufficient to sustain a good mood and higher energy.

Some people experience seasonal affective disorder in the summer. And others who typically have winter depression may notice symptoms during prolonged periods of cloudy or rainy weather during other seasons. You and your doctor can adjust your light box treatment based on the timing and duration of your symptoms.

Sticking with it

With appropriate light therapy, you may start to feel better within several days. In some cases, though, it can take two or more weeks. Sticking to a consistent daily routine of light therapy sessions can help ensure that you maintain those benefits over time. If you interrupt light therapy during the winter months or stop too soon in the spring when you think you're improving, your symptoms could return.

Last Updated: 10/04/2006
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