Atypical depression is a subtype of major depression or dysthymic disorder that involves several specific symptoms, including increased appetite or weight gain, sleepiness or excessive sleep, marked fatigue or weakness, moods that are strongly reactive to environmental circumstances, and feeling extremely sensitive to rejection.
Atypical depression can be a “specifier” for either major depression or dysthymic disorder. People with atypical depression have often experienced depression first at an early age, during their teenage years.
Dysthymic disorder, now known in the psychiatric community as “persistent depressive disorder,” is a condition involving the presence of a depressed mood more days than not for at least a two year period in adults (one year in children and adolescents) plus at least two of the above associated symptoms, but fewer than the five symptoms which define a major depressive episode.
Despite its name, atypical depression is very common. It is contrasted with “melancholic” depression, another subtype of depression, involving symptoms of insomnia (rather than oversleeping), loss of appetite (rather than increased appetite), a relative lack of mood reactiveness to environmental circumstances, and a markedly diminished ability to feel pleasure.