The predominant complaint is excessive sleepiness for at least 1 month as evidenced by either prolonged sleep episodes or daytime sleep episodes that occur almost daily.

The excessive sleepiness causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.

The hypersomnia is judged to be related to another Axis I or Axis II disorder (e.g., major depressive disorder, dysthymic disorder) but is sufficiently severe to warrant independent clinical attention.

The disturbance is not better accounted for by another sleep disorder (e.g., narcolepsy, breathing-related sleep disorder, a parasomnia) or by an inadequate amount of sleep.

The disturbance is not due to the direct physiological effects of a substance (e.g., a drug of abuse, a medication) or a general medical condition.