There are several potential causes of hypersomnia, including:
- The sleep disorders narcolepsy (daytime sleepiness) and sleep apnea (interruptions of breathing during sleep)
- Not getting enough sleep at night (sleep deprivation)
- Being overweight
- Drug or alcohol abuse
- A head injury or a neurological disease, such as multiple sclerosis or Parkinson's disease
- Prescription drugs, such as tranquilizers or antihistamines
- Genetics (having a relative with hypersomnia)
- Depression