It just hits me for the most part - mine effects me as sudden DEEP depression late evenings (8pm) in winter, I'm normally a cheery person so never suffered depression or even felt sad before SAD started effecting me a few years ago...granted now that's a different story. As it's so infrequent I don't do much to prevent it, although I do suspect it may be adding to depression/anxiety at the moment, however...
If I was to do something about it I would firstly address any sleeping issues - ASD folks tend to be lacking in melatonin, which is also linked with SAD, and both are linked with sensitivity to light and environmental changes, so I would focus more on regulating sleeping patterns and most importantly of course is restful sleep. Do everything possible to get good sleeping patterns.
As well as light therapy units have black-out blinds and use the two together, with natural light, to get a good light/dark ratio going to essentially trick the body - plus lots of outdoors when possible. Black-out blinds have been essential for me due to messed-up sleeping patterns, for avoiding street lights in particular...be aware of dark lit rooms in the day or lights shining under his doors at night.
Lots of plants and colour on the walls - okay, I'm going with the colour = happy idea here, but generally speaking it may be of benefit with SAD given as SAD is contributed to by the general miserableness of dull winter months so lots of orange, red and yellow can be helpful plus lots of lush indoor plant, hell paint his bedroom yellow or sky blue!
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Bloodheart
Good-looking girls break hearts, and goodhearted girls mend them.