Have you had enough of winter? Are you ready for the golden days of spring and summer? The shorter days from December to March can bring the curtain down on our moods and well-being. Some people experience a distinct form of depression in winter, Seasonal Affective Disorder (SAD). The disorder is rooted in the interplay between our natural circadian rhythms, the brain chemical melatonin, and the warmth and light of the sun. Melatonin is secreted by the brain's pineal gland, highlighted above in red. The absence of sunlight triggers melatonin production, so most melatonin is naturally produced at night when we are sleeping. When someone is in darkness for longer than usual, it can result in an overproduction of melatonin, which can lead to symptoms of depression. People affected by SAD want to shut down, and spend far more time sleeping. They crave sweet and starchy foods, so many gain weight during the winter. What else is affected by sunlight and warmth? Our circadian rhythms, which control our sleep-wake cycle among other daily cycles. In sleep studies, the moods of many subjects seem to follow the circadian clock, being at the lowest most depressed level when the body's temperature is lowest, and improving as temperature increases. For most SAD sufferers, the return of sunlight and warmer temperatures brings the return of energy and a positive outlook on life.

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