Depression that repeatedly occurs with onset of autumn and winter is to as chronic, low-grade depression is to seasonal affective disorder; dysthymic disorder cyclothymic disorder; seasonal affective disorder bipolar disorder; cyclothymic disorder rapid cycling; flat affect

Depression that repeatedly occurs with the onset of autumn and winter is to seasonal affective disorder as chronic, low -grade depression is to dysthymic disorder. Seasonal affective disorder is a type of depression that is related to changes in seasons such that it begins and ends at about the same times every year. Dysthymic disorder is a smoldering mood disturbance characterized by a long duration as well as transient periods of normal blood. 

Hmmm i'm not sure about this one