It has only been in recent years that the medical profession has diagnosed this winter depression as a treatable disorder. We can't see the sun in Vancouver through the black rain clouds. The answer is simple, affordable and available. To answer your question on the technical side, blood levels of the light sensitive hormone, melatonin, which may be abnormally high at certain times of the day are rapidly reduced by light exposure. Depending on when bright light is presented, the body's internal clock which controls daily rhythms of body temperature, hormone secretion, and sleep patterns, shifts ahead or is delayed when stimulated by light.
Light therapy involves exposure to intense levels of light under controlled conditions.
The recommended light therapy system consists of a set of fluorescent bulbs installed in a box with a diffusing screen and set up on a table or desk top at which one can sit comfortably for the treatment session. Treatment consists of sitting close to the light box, with lights on and eyes open. It is as simple as reading the morning paper and getting a good dose of sunlight at your kitchen table. What is important is to orient the head and body toward the lights, concentrating on activities on the surfaces illuminated by the lights, and not on the lights themselves. Treatment sessions can last from 15 minutes to three hours once or twice a day depending on the equipment used and individual needs.