Final answer:
Many individuals with seasonal affective disorder (SAD) have a gene mutation affecting their circadian rhythms, which are regulated by melatonin produced by the pineal gland. Reduced winter sunlight disrupts melatonin cycles, contributing to SAD symptoms. Light therapy is an effective non-drug treatment for SAD. Therefore, the correct option is A
Step-by-step explanation:
Many people with seasonal affective disorder (SAD) have a mutation in one of the genes responsible for regulating circadian rhythms. Circadian rhythms are the physical, mental, and behavioral changes that follow a daily cycle, responding primarily to light and darkness in an organism's environment. One important regulator of these rhythms is the pineal gland, which secretes the hormone melatonin. Melatonin release is stimulated by darkness and inhibited by light, and it influences sleep-wake cycles. In the context of SAD, the reduced sunlight in winter months can disrupt the normal cycle of melatonin production, leading to symptoms such as increased appetite, sluggishness, and increased sleepiness.
A possible non-drug therapy for SAD includes light therapy, which involves exposure to artificial light that mimics natural sunlight. This can help in normalizing the disrupted circadian rhythms in SAD patients. Tailoring the exposure to blue light, which is particularly effective in influencing circadian rhythms, is often used in light therapy regimens.