Somnolence (or "drowsiness") is a state of near-sleep, a strong desire for sleep, or sleeping for unusually long periods (c.f. hypersomnia). It has two distinct meanings, referring both to the usual state preceding falling asleep, and the chronic condition referring to being in that state independent of a circadian rhythm. The disorder characterized by the latter condition is most commonly associated with users of prescription hypnotics, such as mirtazapine or zolpidem.

It is considered a lesser impairment of consciousness than stupor or coma.

Hazards

Sleepiness can be dangerous when performing tasks that require constant concentration, such as driving a vehicle. When a person is sufficiently fatigued, he or she may experience microsleeps (loss of concentration).

Associated conditions

• atypical depression
• bruxism
• sleep apnea
• sleep deprivation / insomnia
• advanced sleep phase syndrome
• narcolepsy
• clinical depression, especially seasonal affective disorder or SAD
• infectious mononucleosis (glandular fever)
• Paget's disease
• increased intracranial pressure for example due to brain tumors
• brain edema
• stroke
• traumatic brain injury
• Intracranial hemorrhage such as due to ruptured aneurysm
• hydrocephalus
• cerebral hypoxia
• encephalitis - (viral, bacterial or other agents)
• Lyme disease (borreliosis)
• hypothyroidism
• starvation
• hypothermia
• medications
  • tranquilizers / hypnotics especially benzodiazepines such as temazepam (Restoril®) or nitrazepam (Mogadon®) and barbiturates such as amobarbital (Amytal®) or secobarbital (Seconal®)
  • antidepressants - for instance sertraline and venlafaxine.
  • antipsychotics - for example: thioridazine, quetiapine, and olanzapine (Zyprexa) but not haloperidol.
  • analgesics - mostly prescribed or illicit opiates such as Oxycontin or heroin
  • HIV medications - for example: Sustiva and medications containing efavirenz
  • anticonvulsants / antiepileptic - such as phenytoin (Dilantin), carbamazepine (Tegretol), lamotrigine (Lamictal) (see article on Epilepsy.com)
  • antihistamines - for instance diphenhydramine (Benadryl)
  • hypertension medications such as Norvasc
  • generally many other agents with impact on central nervous system in sufficient or toxic doses

See also

• Insomnia
• Hypersomnia
• Dyssomnia
• Fatigue (physical)