Does seasonal affective disorder subside in more temperate climates?
Although exceptions to the rule have been reported in some surveys, in general SAD hits more people the further north they live (in the northern hemisphere).
For example, one major study projected 5 times as much SAD in New England than in Florida. An implication is that a SAD sufferer might do well to move south.
Problem is, that doesn't guarantee problem-free winters, since a fraction of the population still develops symptoms down south.
Before you move, you should test your selected destination with an extended winter stay -- not just a one-week get-away!