wow. it sounds just like me. i have chronic major depression. i've had it for a very long time. and the way you described the need for naps and sleep is just like mine. some people just don't understand this at all. physical activities actually makes this worse, since i get burned out easily and just conk out for hours. i know this is one weird symptom, and it's possible that there's something about it that doctors and scientists have not discovered. i'm educated to the level of a scientist, and i don't believe sleep/napping is the cause but a symptom. yes, it can be a vicious cycle. we have to find a treatment for the core cause without the sleepiness side effects. funny, sunlight makes me sleepy as heck, and that's a contradiction to a healthy daylight exposure.