Persons with mood illnesses are more sensitive to light than others. Too much light causes manic symptoms, too little light causes depressive symptoms. In the spring and summer there is too much light, in the fall and winter there is not enough light. You thus need to modulate your light exposure to avoid causing mania in the spring and summer and depression in the fall and winter. Mood episodes go together, so if you want to prevent winter depression, you should also try to prevent summer mania.
For the fall-winter (September-January):
In the winter, there is not enough light. Therefore you will sleep in the morning longer than you should, and that will throw off your circadian rhythms. You therefore need to increase your light exposure.
Use indirect light; do not look into the light box directly (treat it like the sun). Have it on the table while you read or eat in the morning. Dose is 25- 30 minutes to one hour as long as depression persists. Use the lightbox daily initially, and then reduce use to every other day for prevention. Use the lightbox in the morning (before 10 AM): remember you are trying to replace the morning sunlight which goes away in the winter.
For the spring/summer (March-August):
In the summer, there is too much light. Therefore you will sleep in the morning less than you should, and that will throw off your circadian rhythms. You therefore need to decrease your light exposure
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