This is useful, and interesting. We think we're so "civilized" and that we control our bodies -- ha! Kay Jamison's book "Touched with Fire" (about manic-depression and the link to creativity and genius) touches on this. I haven't read the book in some years, but my memory is that there's a theory that we were once ALL "manic-depressive," that there were societal and behavioral patterns that were once normal, a kind of feast/famine, revel/hibernate mentality. Often the cycles ofmanic-depressives mimic the seasons, or have a seasonal regularity.

My layman's view of this (I've read tons about manic-depression for a project I did, but am not a clinician) is that there are dozens of kinds of depression that some day will be recognized as separate diseases. Right now they're all dumped into one black hole, as it were. SAD is one of the first to be pulled out and looked at. Common sense (which often doesn't apply in science, I nkow) would say that LIGHT MATTERS!

(I posted elsewhere about light therapy in Scandinavia, where they've come up with a window that mimics sunlight, that has been successful in treating SAD.)