As usual, when I started researching the origins of Groundhog Day, I instantly zipped down the nearest rabbit hole like Alice. Apparently, the tradition of using an animal as a weather forecaster is quite ancient. A variety of animals have been employed...bears, snakes, badgers. Similar customs have been reported across the northern hemisphere--and even from some places in the southern hemisphere (for their spring). The groundhog day celebrations in Pennsylvania were introduced by German immigrants in the 1700s.
The holiday has also been associated with Candlemas, Imbolc, St. Brigid's Day, and a number of other very early pagan celebrations. This day was seen as the day when "light" was more prevalent than the "dark" of winter.
For that reason, perhaps sufferers of SADS should celebrate this turning of the season! In any case, Happy Groundhog Day!