Too much psychology

The DSM-IV-TR, a widely used manual for diagnosing mental disorders, defines Atypical Depression as a subtype of depression or dysthymia, characterized by Atypical Features:

A. Mood reactivity (i.e., mood brightens in response to actual or potential positive events)
B. At least two of the following:
Significant weight gain or increase in appetite ("comfort eating")[3]
Hypersomnia (sleeping too much, as opposed to the insomnia present in melancholic depression)
Leaden paralysis (i.e., heavy, leaden feelings in arms or legs)
Long-standing pattern of interpersonal rejection sensitivity (not limited to episodes of mood disturbance) that results in significant social or occupational impairment
C. Criteria are not met for Melancholic Depression or Catatonic Depression during the same episode.
By the ICD-10 classification, it will fall in the category of F32 or F39.