"The intake of sweets may either act on similar neurochemical substrates to those affected by light or provide a behavioral marker for individuals susceptible to light response."
"As part of their winter depressions many SAD patients suffer from a reversible
form of obesity."
"Humans, however, naturally increase the length of their photoperiod by the use of artificial lighting. If the seasonal changes in eating and weight described above are influenced by photoperiod , how is it that they persist despite the use of artificial lighting? The first clue to resolving this paradox came from the observation of Lewy and colleagues, that whereas the nocturnal secretion of melatonin by the pineal gland could be suppressed by artificial light in animals, it required light of far higher intensity (2500 lux) to suppress nocturnal melatonin secretion in humans. It was this finding that inspired the treatment of patients with SAD by extending their winter photoperiod with bright artificial light."