Final answer:
Melatonin is believed to play a role in Seasonal Affective Disorder (SAD) by disrupting sleep-wake cycles due to prolonged darkness in winter months. Light therapy can act as a non-drug therapy to reduce SAD symptoms, and improvements are often observed within two weeks, although this can vary between individuals.
Step-by-step explanation:
Seasonal Affective Disorder (SAD) is recognized for causing an increased appetite, sluggishness, and increased sleepiness, particularly during the low-light winter months. Melatonin, a hormone produced by the pineal gland, is known to regulate sleep-wake cycles and its production is affected by light exposure. Researchers propose that the extended hours of darkness in winter may lead to overproduction of melatonin, contributing to SAD symptoms.
A widely recognized non-drug therapy for SAD is light therapy. It involves exposure to bright artificial light, often from a light box, which is used to mimic natural outdoor light and is believed to cause a chemical change in the brain that lifts mood and eases other symptoms of SAD. The effectiveness of light therapy can vary; some people see improvements in their SAD symptoms within a few days, while for others it might take a few weeks. On average, it can take about two weeks for light therapy to significantly decrease SAD symptoms.