dr. joshua weiner joins us to explain.anged oush clocks, i guess it's been a week or so, and so now we're dealingwith dark skies. i mean, it's dark out there when we go home. so, is i the darkness or is it the co that makes people depressed this time of year? >> it's the darkness. so, one of the theories as to why people develop seasonal affective disorder, which is essentially depression during late fall, early wince, is that the decrease in daylight impacts your circadian rhythm or body's biological clock that has affects on melatonin level and effects on yourer is tone er ie level. in this area 1% of people will develop seasonal affective disorder. about 15% or 20% will develop the winter blues. there's a significant difference between the two. with the winter blues you're feeling bummed out, low frg. but with seasonal affective disorder you are experiencing major depressive disorder. >> what about people who work strange hours, who have to sleep most of the day and get up in the night to work. i mean, they must have th