Elizabeth Saenger, PhD
Bipolar depression is typically a very serious phase of bipolar disorder, and yet appealing options for therapy are limited. (To see what choices are best under what circumstances, consult the Algorithm for Bipolar Depression at Harvard Medical School.)
The FDA has not approved any antidepressants for the treatment of bipolar depression even though physicians often prescribe these drugs out of desperation.
Unfortunately, antidepressants may create problems, since they can:
- kick off hypomania (a state like mania, only not quite as severe)
- lead to rapid cycling (four or more episodes per year) or worsen the course of the disorder
- lack effectiveness.
However, there may be hope for the many people with bipolar disorder whose symptoms relate to their circadian rhythms. These symptoms include:
- sleeping much more than usual
- an inability to go to sleep until much later than usual
- increased eating.
Preliminary data suggest that when these four symptoms of bipolar depression occur together, light therapy would be effective.
Putting an Idea to the Test
Dorothy K. Sit, MD, and her colleagues tested the idea that daily bright light therapy at midday might be a great add-on treatment for bipolar depression. They randomly assigned people with that condition to one of two conditions: bright vs dim red light at midday. Each person received a six-week course of treatment, and the experimenters made sure the subjects were adhering to the protocol by installing a light sensor inside the light box.
In short, with this, and other, precautions, the experimenters ensured their study met the gold standard of research design.
The Triumph of Light Therapy
Unsurprisingly, this larger, well-designed experiment supported the results of smaller, fragmented, and sometimes seemingly inconsistent studies. Specifically:
- 68% of those exposed to bright light therapy experienced a disappearance of their symptoms vs 22% of those exposed to the placebo (the dim red light)
- sleep quality improved in both groups
- no one in either group switched from depression into hypomania or mania.
In short, it seems that bright light (vs dim red light) in midday was a clear winner. Figuring out how to perfect this winner, perhaps with changes in when the light therapy is given, is a controversial challenge for the future.