Final answer:
Seasonal affective disorder (SAD) is the tendency to experience depression during winter months due to changes in light exposure that affect melatonin levels. Light therapy is a non-drug treatment that helps regulate these levels. Vitamin D deficiency may also play a role in SAD.
Step-by-step explanation:
The term seasonal affective disorder (SAD) refers to the tendency of some persons to reliably become depressed during the winter months. Seasonal affective disorder is a mood disorder characterized by increased appetite, sluggishness, and increased sleepiness. It occurs most commonly during the winter months, especially in regions with long winter nights. Melatonin, a hormone that regulates sleep and wakefulness, plays a role in SAD; its production is influenced by the amount of light a person is exposed to. Therefore, less sunlight in the winter months can lead to an overproduction of melatonin, contributing to the symptoms of SAD.
A non-drug therapy for seasonal affective disorder is light therapy, which involves exposure to bright artificial light that mimics natural outdoor light. Light therapy can help regulate melatonin levels and improve mood in individuals with SAD. Another component to consider is a possible deficiency in vitamin D, which has also been linked to this disorder, more common in individuals with darker skin pigmentation.