It’s that time of year when days are getting noticeably shorter and daylight savings time is ending. That means for the northern U.S., the sun will soon be setting around 4:00 in the afternoon with total daylight at less than nine hours.

Winter weather also usually means staying indoors more. Without enough natural sunlight exposure, the risk for seasonal depression increases. Previous research has shown that bright light therapy can be effective at treating seasonal affective disorder. New research is showing that it has the potential to help treat bipolar disorder as well.

Approximately 25% of people with bipolar disorder, especially those with bipolar II, report that their symptoms fluctuate with the seasons. For these people, it’s common to experience depression throughout the winter, possibly with no reprieve until spring. The symptoms of seasonal depression are the same as depression experienced any other time:

  • Depressed mood
  • Loss of interest or pleasure
  • Significant weight loss or gain
  • Sleep disturbances
  • Psychomotor agitation
  • Fatigue
  • Feelings of worthlessness or hopelessness
  • Diminished ability to concentrate
  • Thoughts of death or suicide

Treatment for depression is typically made up of a combination of medication and therapy. Now, there is growing research showing that bright light therapy may also be effective in treating depression in bipolar disorder.

One new study looked at 63 patients to see what their reaction to bright light therapy would be. All patients were on psychotropic medications and were experiencing depressive symptoms. Thirty-three patients were exposed to bright light therapy (10,000 lux) while the controls were exposed to dim red light therapy. Participants were exposed to light therapy for one hour per day, every morning for two weeks.

At the end of the two-week period, 78% of participants who were exposed to bright light therapy reported an improvement in symptoms, compared to 43% with dim red light therapy. The response was higher among women than men. Median time for response to the light therapy was approximately four days. No one experienced hypomanic or manic symptoms following the experiment.

Another recent study looked at 46 participants with bipolar disorder, half of whom were exposed to bright light therapy (7,000 lux), the other half to dim red light therapy (50 lux) every day at midday. Participants were titrated up to one hour per day in fifteen minute increments. Depressive symptoms were measured weekly over a period of six weeks.

At the end of the six-week period, 68% of the participants exposed to bright light therapy achieved remission, compared to only 22% who received dim red light therapy. The greatest effect seemed to be achieved between weeks four and six. Sleep quality improved in both groups. There were no reports of polarity switching.

When performing light therapy at home, there are important steps to take.

  • The light must be at 7,000-10,000 lux to be effective.
  • The light must be kept close to the face.
  • Do not look directly into the light.
  • Timing should start at 15 minutes per day and titrate up to one hour per day over the course of several days or weeks.
  • Avoid exposure to light therapy in the evening so that sleep is not disturbed as sleep disturbance may increase the risk of switching to hypomania or mania.

Anyone attempting bright light therapy should contact their doctor to make sure they are monitored carefully during the process, as there has been previous research showing that a switch from depression to hypomania is possible.

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Image credit: Norland Zhang