May. January and February are often the most difficult months. The average length of depression is about five months but varies a lot. Depression in general, and SAD specifically, sometimes runs in families. The timing, duration and distance of the lights vary from person to person and should be determined by a knowledgeable professional, and is sometimes adjusted as treatment continues. While the person is in front of the light they don't have to look directly into the light, and may do things such as read, write, or have breakfast.
Many people feel a dramatic improvement in mood within three to four days.
The morning light treatments continue throughout the winter, since one often develops problems again if they stop treatments too early in the season. How Phototherapy works, and why people get depressed in the winter, is still not clear, but research indicates some probable answers. One important influence on our internal clocks is the duration, timing, and intensity of sunlight, which changes according to the season. Unfortunately society and its obligations don't necessarily change as well. The time we have to wake up each morning usually stays the same, but our body's clock changes as the time of sunrise changes.