A seasonal pattern of symptoms is most likely to be a characteristic of bipolar disorder.
Bipolar disorder is a brain disorder that causes unusual changes in mood, activity levels and energy. The mood ranges from manic episodes to a depressive ones. Seasonal pattern represents a potentially important specifier of bipolar disorder. Studies indicate that seasonality may reflect increased severity of disorder.
There are four types of bipolar disorder: Bipolar I, Bipolar II, Cyclothymic, Other Specified and Unspecified Bipolar.