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Somnolence

What Is It, Causes, Treatment, and More

Author: Ali Syed, PharmD

Editors: Alyssa Haag,Emily Miao, PharmD,Kelsey LaFayette, DNP, RN

Illustrator: Jessica Reynolds, MS

Copyeditor: David G. Walker

Modified: 29 Jun 2022


What is somnolence?

Somnolence, defined as a state of drowsiness or strong desire to fall asleep, may be characterized as either a benign symptom, such as a state of drowsiness prior to falling asleep or, most commonly, as a symptom of an underlying condition, such as a sleep disorder, anxiety, depression, or stress.

Depending on the underlying disease, disorder, or condition, individuals experiencing somnolence may also present with other symptoms, such as changes in mood, personality, or behavior; impaired memory; lethargy; and weakness. Individuals that present with somnolence alongside a change in consciousness, inability to get warm, confusion, hallucinations, seizures, severe headaches, or stiff neck require urgent medical attention.

What is the difference between fatigue and somnolence?

Somnolence is characterized as a state of sleepiness in which an individual may be cognitively impaired and lack the ability to pay attention. Fatigue, on the other hand, is characterized by mental and/or physical exhaustion as well as low energy without the cognitive impairment seen in somnolence

Somnolence increases with inactivity and rest and is commonly followed by sleep. It can be dangerous in certain situations where attention and alertness is required, such as operating a vehicle.

Fatigue is increased with activity, particularly if long in duration and intensity, such as physical exercise. It is also commonly alleviated by inactivity and rest and does not usually prove to be dangerous.

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What causes somnolence?

Somnolence may be caused by a variety of factors, including acute and chronic medical conditions, medications, and lifestyle factors.

Acute medical conditions, such as electrolyte disorders (e.g., hyponatremia or hypomagnesemia), head injuries, hypothermia, and infections (e.g., mononucleosis or meningitis) may serve as an underlying cause of somnolence. Chronic medical conditions, such as chronic fatigue syndrome, fibromyalgia, obesity, depression, anxiety, diabetes, chronic pain, and hypothyroidism may also contribute to somnolence. Sleep-wake disorders, such as insomnia, sleep apnea, narcolepsy, restless leg syndrome, or delayed sleep phase disorder are also characterized by somnolence.

Several medications, including antihistamines, benzodiazepines, hypnotics, opioids, antidepressants, anticonvulsants, and antipsychotics, may precipitate somnolence, particularly in the event of a medication overdose. Alcohol intoxication may also cause somnolence.

Lifestyle factors, such as overworking, irregular work schedule, jet lag, and stress, may also lead to somnolence.

How is somnolence treated?

Treatment of somnolence depends on the underlying cause. Since the exact cause of somnolence may be due to a combination of factors, diagnosis by a healthcare professional may include a variety of techniques, including a thorough review of systems and medical history followed by a conduction of a physical exam and imaging or laboratory tests.

In some cases, imaging, such as a computed tomography (CT) scan or an electroencephalogram (EEG), may be performed to rule out any potential brain abnormalities causing somnolence. An electrocardiogram (ECG) may also be performed to rule out any cardiac abnormalities contributing to somnolence. Laboratory tests, such as blood and urine samples, may also be used.

Prevention of somnolence may be achieved by controlling common underlying causes. In cases where somnolence is due to lifestyle factors, non-pharmacological treatment options, such as rest, meditation, mindfulness exercises, counseling, and cognitive behavioral therapy (CBT), may be explored. Somnolence due to an underlying medical condition or medication is commonly cured once the underlying medical condition is treated or the offending medication is modified. Left untreated, complications of somnolence may include depression, inability to perform daily tasks, and a poor quality of life.

What are the most important facts to know about somnolence?

Somnolence is defined as a state of drowsiness or strong desire to fall asleep and is commonly associated with an underlying condition. Somnolence is characterized as a state of sleepiness in which an individual may be cognitively impaired and lack the ability to pay attention, whereas fatigue is characterized by mental or physical exhaustion as well as low energy. Depending on the underlying condition, somnolence may also present with various other symptoms. Somnolence may be caused by a variety of factors, including acute and chronic medical conditions, medications, and lifestyle factors. Diagnosis and treatment depends on the underlying cause, and may involve imaging and laboratory tests as well as pharmacological and non-pharmacological measures.

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Related links

Sleep disorders: Clinical practice

Resources for research and reference

Daytime Drowsiness. In Harvard Health Publishing. Retrieved February 27, 2022, from https://www.health.harvard.edu/decision_guide/daytime-drowsiness

Peters, B. (2020). Differences Between Sleepiness and Fatigue. In Verywell Health. Retrieved February 27, 2022, from https://www.verywellhealth.com/sleepiness-fatigue-difference-3973906

Singareddy, R., Bixler, E. O., & Vgontzas, & A. N. (2010). Fatigue or daytime sleepiness?. Journal of Clinical Sleep Medicine, 6(4): 405. DOI: 10.5664/jcsm.27885

Sleepiness vs. Fatigue: What’s the Difference?. In Live Well Wellness Center. Retrieved February 26, 2022, from https://www.livewellwellnesscenter.com/blog/sleepiness-vs-fatigue-whats-the-difference

What’s the difference between fatigue and drowsiness?. (2020). In Optalert. Retrieved February 26, 2022, from https://www.optalert.com/whats-the-difference-between-fatigue-and-drowsiness/