somnolence

physiology

Also known as: drowsiness

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July 14, 2026

Quick Summary

Somnolence refers to the state of being drowsy or sleepy. It is the quality or state of needing or desiring sleep. Related terms include sleepiness, drowsiness, and lethargy. Conversely, antonyms for somnolence are wakefulness and alertness.123

Somnolence can also describe something that tends to cause sleep, such as a soporific or hypnotic effect. While sleep is a vital physiological function for repair, memory consolidation, and overall health, excessive sleepiness can be a symptom of various sleep disorders, including hypersomnia and circadian rhythm disorders.3456

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Neural theories
…from sensory input, demonstrated chronic somnolence. It has been reasoned that a similar cutting off of sensory input, functional rather than structural, must characterize natural states of sleep. Other supporting observations for the stimulus-deficiency theory of sleep included presleep rituals such as turning out the lights, regulation of stimulus input,…
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…from sensory input, demonstrated chronic somnolence. It has been reasoned that a similar cutting off of sensory input, functional rather than structural, must characterize natural states of sleep. Other supporting observations for the stimulus-deficiency theory of sleep included presleep rituals such as turning out the lights, regulation of stimulus input,…
Read More