I've often wondered if SAD is distinctly different from just feeling worse due to the weather. I've often wondered if the SAD condition is really just a cutoff point on a continuum, where all of us feel slightly worse with each increment of declining weather. Then, the psychologists decide on an arbitrary cutoff point to say, "There, you are SAD there!"
Frasier and co all looked happy to me, despite their family troubles I know that sitcom was Seattle based. Does it have a great big snow topped mountain on the horizon too, from memory?