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Medical and Brain Conditions That Cause Excessive Sleepiness

Eric Suni

Written by

Eric Suni, Staff Writer

Dr. Abhinav Singh

Medically Reviewed by

Dr. Abhinav Singh, Sleep Physician

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Uncontrollable yawning, heavy eyelids, and the powerful urge to doze off during the day are signs of excessive sleepiness. Struggling to stay awake can drag down performance at school and work, put strain on social and personal relationships, and create serious risks when driving.

If you experience persistent drowsiness, it’s normal to wonder, “why am I always sleepy?”

The most common causes of excessive sleepiness are sleep deprivation and disorders like sleep apnea and insomnia. Depression and other psychiatric problems, certain medications, and medical conditions affecting the brain and body can cause daytime drowsiness as well.

Recognizing excessive daytime sleepiness (EDS) is a first step toward addressing the problem. Working with a doctor to identify its cause and improve sleep habits can enhance your daily productivity, mood, and overall health.

What Is Excessive Daytime Sleepiness?

Excessive daytime sleepiness is a difficulty staying awake or alert when you need to. Many experts define EDS as distinct from fatigue, which involves strong feelings of physical exhaustion, but the two conditions may overlap.

Infographic explaining that 166 million people in the U.S. feel unrested most of the week and 103 million find this drowsiness affects daily activities

Recent research points to excessive sleepiness being a significant problem. The Sleep in America Poll for 2020 by the National Sleep Foundation found that nearly half of Americans report feeling sleepy between three and seven days per week.Forty percent of adults said that their drowsiness interferes with daily activities at least occasionally.

Some resources refer to EDS as hypersomnia, which describes disorders of excess sleep. However, hypersomnia is a broader term that includes issues like sleeping too much at night that are distinct from extreme drowsiness during the day or in situations when alertness is required.

What Are the Causes of Excessive Daytime Sleepiness?

Excessive daytime sleepiness is not a condition in itself; instead, it is a symptom caused by an underlying problem.

Sleepiness Caused by Sleep Deprivation

Lack of sleep is widely considered to be the most common cause of excessive sleepiness. Sleep deprivation may be short-term or chronic and can itself be caused by numerous sleep disorders and other medical conditions:

  • Failure to Prioritize Sleep: Choosing to stay up late to watch a series or wake up early to go to the gym are examples of how sleep can get bumped down the list of priorities and crowded out of a busy schedule. This can cause drowsiness the next day, and the problem can accumulate over time. When these choices cause lack of sleep over an extended period of time, it is known as insufficient sleep syndrome.
  • Insomnia: This condition includes a range of problems that make it hard to fall asleep or stay asleep for as long as you want. Insomnia is often related to other sleep problems described here that give rise to excessive sleepiness.
  • Sleep Apnea: Obstructive sleep apnea (OSA) is a breathing disorder characterized by brief pauses in breathing during the night. It creates fragmented sleep that typically causes daytime drowsiness and may affect up to 20% of adults. Central sleep apnea (CSA) is less common but can also cause disturbed sleep.
  • Restless Leg Syndrome (RLS): This condition causes a strong sensation of needing to move one’s extremities, particularly the legs, and is a known risk for disrupting total sleep time and sleep quality.
  • Circadian Rhythm Sleep-Wake Disorders: When a person’s sleep schedule is misaligned with their local day-night cycle, it can cause short and fragmented sleep. Examples include jet lag and sleeping problems among shift workers.
  • Poor Sleep Quality: Sleep insufficiency isn’t just about a low quantity of sleep; it’s also about sleep quality. People who don’t smoothly progress through sleep cycles may fail to get enough deep sleep or REM sleep. As a result, they may not wake up refreshed even if they sleep for the recommended number of hours.
  • Frequent Nighttime Urination: This condition, known as nocturia, involves needing to get up from bed during the night to pee and is estimated to affect up to one out of three older adults and one out of five younger people.

Sleepiness Caused by Other Medical and Brain Conditions

A lack of sleep is not the only potential cause of excessive sleepiness. Medications, especially sedatives, can make a person drowsy and disoriented during the day. Antidepressants, pain medications, and over-the-counter antihistamines are just a few of the other types of medications that can cause sleepiness. In addition, withdrawal from some drugs may provoke drowsiness.

Mental health disorders can frequently cause drowsiness. For example, it is believed that nearly 80% of people with major depression have excessive daytime sleepiness. Bipolar disorder, post-traumatic stress disorder (PTSD), and general anxiety disorder are associated with sleeping problems that may give rise to bouts of excessive sleepiness.

Several brain conditions can cause excessive daytime sleepiness. Narcolepsy is a prominent example as it is a neurological condition in which the brain cannot properly regulate the sleep-wake cycle. Narcolepsy affects around one in every 2,000 people and makes them prone to falling asleep rapidly, including at inopportune times.

Neurodegenerative diseases including dementia and Parkinson’s Disease are tied with sleeping difficulties and daytime drowsiness. Traumatic brain injury (TBI) and concussions commonly cause sleeping problems, and brain tumors or lesions may provoke excessive sleepiness. Infections, including meningitis and those that cause encephalitis (swelling of the brain), can also lead to EDS.

Neurodevelopmental disorders like attention-deficit/hyperactivity disorder (ADHD), which affects millions of children and adults, cause a range of sleeping problems including daytime sleepiness. Up to 31% of children with Autism Spectrum Disorders (ASD) have been found to have daytime sleepiness, and sleeping issues may persist into adulthood for people with these neurodevelopmental disorders.

Other health problems beyond brain conditions can make a person sleepy during the day. Metabolic problems, including diabetes and hypothyroidism, can be risk factors for drowsiness. Medical conditions like anemia, abnormal blood sodium levels, and electrolyte imbalances can also provoke excessive sleepiness.

Getting Relief for Excessive Daytime Sleepiness (EDS)

Relief is possible for most people with excessive sleepiness. The optimal treatment is tailored to each person based on the specific cause or contributing factors.

Because EDS can be caused by both poor sleep habits and medical and brain conditions, there are a diverse range of approaches to resolving it. A doctor is in the best position to identify and tailor optimal treatment pathways for individuals.

If drowsiness is derived from sleep deprivation, various steps can be taken to improve sleep quality and quantity. Examples include continuous positive airway pressure (CPAP) machines for sleep apnea and cognitive behavioral therapy for insomnia (CBT-I). Many sleep-focused treatments will help facilitate improvements to sleep hygiene, which incorporates a person’s sleep habits and bedroom environment, and whether they’re using the best mattress and pillow for their needs.

If EDS is tied to another medical problem, treatment typically focuses on resolving that underlying issue. Sleep hygiene improvements may be encouraged along with other treatments to help people incorporate healthy sleep tips into their daily routines.

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About Our Editorial Team

Eric Suni

Staff Writer

Eric Suni has over a decade of experience as a science writer and was previously an information specialist for the National Cancer Institute.

Dr. Abhinav Singh

Sleep Physician


Dr. Singh is the Medical Director of the Indiana Sleep Center. His research and clinical practice focuses on the entire myriad of sleep disorders.


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