Why Do I Wake Up Tired After A Full Night?

Total hours spent lying in bed do not equal total hours of restorative sleep. You can spend eight full hours under the covers, remain unconscious the entire night, and still wake up exhausted because your brain failed to complete its necessary cycles of deep slow-wave sleep and rapid eye movement sleep.

When you wake up tired after sleeping what seems like a full night, the problem rarely stems from a lack of time. It stems from factors that degrade the structural quality of your sleep, shift your biological timing, or trigger subtle physical awakenings that your conscious memory discards before sunrise.

Understanding why you feel unrefreshed after sleep requires looking beyond total duration. By examining how your body cycles through sleep stages, how your internal clock operates, and how subtle disturbances interrupt your rest, you can pinpoint why your nights fail to restore your energy.

Waking up tired after a full night usually stems from poor sleep architecture, hidden awakenings, or circadian mismatch rather than a lack of hours. Factors like micro-arousals, alcohol consumption, breathing disturbances, and waking from deep sleep prevent your brain from spending adequate time in restorative sleep stages.

Why sleeping 8 hours but tired still happens

Sleep is an active neurological process composed of distinct stages, not a uniform state of unconsciousness. During a healthy night, your brain moves back and forth between light stage 1 and stage 2 sleep, deep slow-wave sleep, and rapid eye movement (REM) sleep in predictable cycles lasting roughly ninety to one hundred and twenty minutes.

If your sleep architecture is distorted, you can stay unconscious for a full eight hours while missing out on the specific stages that restore your physical and mental energy. Deep slow-wave sleep, characterized by high-amplitude delta brain waves, is the phase where human growth hormone is released, tissue repair occurs, and the brain’s glymphatic system clears metabolic waste products accumulated during waking hours. REM sleep consolidates memories, processes emotional experiences, and restores neural plasticity for cognitive performance.

When factors like chronic stress, late meals, subtle noises, or elevated temperature interrupt these cycles, your brain spends an excessive proportion of the night in light sleep. Stage 1 and stage 2 sleep protect sleep continuity but lack the physiological depth required to clear cellular waste or rebuild metabolic energy reserves. You wake up feeling as though you barely slept because light sleep cannot perform these heavy biological recovery tasks. To understand how duration differs from depth, explore our detailed breakdown on sleep quality vs sleep quantity.

For some individuals, spending eight or nine hours in bed while sleeping poorly prompts them to stay under the covers even longer in an effort to regain energy. Forcing additional time in bed when sleep is already fragmented actually dilutes sleep efficiency, leading to lighter, more broken rest across a wider window. If spending eight hours in bed yields persistent grogginess, extending that time to nine or ten hours often worsens the problem. Instead, stabilizing your sleep window to match your actual average sleep time helps consolidate brain wave activity into deeper, unbroken stages.

How sleep fragmentation disrupts your rest without you knowing

One of the most common causes of unrefreshing sleep is sleep fragmentation caused by micro-arousals. A micro-arousal is a brief shift in brain wave activity toward a waking state, lasting anywhere from three to fifteen seconds.

These micro-arousals trigger a sudden surge in sympathetic nervous system tone, causing your heart rate to jump, your blood pressure to rise, and your muscular system to tense. Because these shifts are brief and immediately followed by a return to sleep, your conscious brain does not fully wake up, and your brain fails to form long-term memories of the event due to retrograde amnesia for brief awakenings.

Even though you believe you slept straight through the night without interruption, these repeated disruptions force your brain out of deep slow-wave sleep back into stage one light sleep. A night punctuated by dozens of micro-arousals leaves you with fragmented sleep architecture, explaining why you can wake up tired after sleeping without remembering a single awakening.

Using earplugs or eye masks to block external noise and light is a standard approach to preventing micro-arousals, but this strategy fails when micro-arousals are driven by internal physiological signals. Internal triggers like gastroesophageal reflux, muscle twitches, joint pain, or subtle bladder pressure cause the central nervous system to shift into a lighter state without requiring external sound or light. If blocking external sensory input does not reduce morning grogginess, looking at internal autonomic triggers—such as shifting evening meal composition, adjusting sleep posture, or addressing localized body discomfort—is necessary to stop hidden micro-arousals.

Why do I wake up exhausted even when I slept through the night

When you sleep, your central nervous system relies on uninterrupted progression through every phase of the sleep cycle. The earliest cycles of the night contain the highest concentration of slow-wave sleep, while the final cycles near morning contain longer periods of REM sleep.

If an underlying issue prevents your brain from remaining in slow-wave sleep during the first half of the night, your physical body misses its primary window for muscle tissue repair, protein synthesis, and cellular waste clearance. You wake up with physical heaviness, muscle soreness, and reduced physical stamina during morning movement.

Conversely, if REM sleep is suppressed or fragmented during the second half of the night, your central nervous system misses out on essential neural maintenance. This leads to morning brain fog, emotional reactivity, slowed working memory, and difficulty sustaining focus during daytime tasks. Waking up exhausted after sufficient hours is a classic sign that your brain was forced out of these critical deeper stages.

When morning exhaustion persists despite eight hours of continuous rest, simply lying still in bed longer during the morning will not restore missed deep sleep stages. Once your internal biological clock signals morning wakefulness, your brain wave activity shifts away from deep slow-wave production, meaning extra time spent resting in bed yields only shallow, low-value sleep. Instead of staying under the covers, getting out of bed at a set time and building homeostatic sleep drive throughout the day helps anchor deeper sleep stages during the following night.

The role of slow-wave sleep in physical recovery

During slow-wave sleep, high-amplitude delta waves dominate cortical brain activity, heart rate and respiration drop to their lowest daily levels, and blood flow shifts heavily toward skeletal muscles. The pituitary gland releases human growth hormone, stimulating tissue repair and cellular recovery. Without sufficient slow-wave sleep, your body fails to rebuild energy reserves, regardless of how long you lie still.

The role of REM sleep in mental clarity

During REM sleep, brain wave activity accelerates to frequencies similar to waking hours, while voluntary skeletal muscles are actively inhibited through brainstem motor pathways. Neurotransmitter levels shift, with acetylcholine rising and norepinephrine dropping, creating an environment that allows the brain to process complex emotional experiences and consolidate learning. Suppressing REM sleep leaves you feeling mentally drained and unfocused the following morning.

How your body clock creates a timing mismatch

Your body relies on a master internal clock located in the suprachiasmatic nucleus (SCN) of the brain to synchronize hormone production, core body temperature, and cellular metabolism with the 24-hour solar day. This biological rhythm dictates when your body expects to sleep and when it prepares to wake up.

If your chosen sleep schedule conflicts with your internal biological clock, you experience a circadian timing mismatch. Sleeping eight hours at a time that does not align with your natural circadian phase yields far less restorative value than sleeping those exact same hours when your body naturally expects to rest.

For example, shifting your bedtime back by several hours on weekends creates a state known as social jetlag. Your body attempts to sleep during a phase when core body temperature is beginning to rise and morning cortisol levels are increasing, leading to broken, shallow sleep that leaves you groggy.

Attempting to resolve a circadian timing mismatch by forcing yourself to go to bed early often fails. When you lie down during your circadian “wake maintenance zone”—the period shortly before your body’s natural sleep onset window—your core body temperature remains elevated and your brain produces minimal sleep-promoting neurochemicals. Lying awake in the dark trying to force sleep increases autonomic frustration, raising your heart rate and delaying sleep even further.

Instead of forcing an early bedtime, the standard approach for realigning a circadian mismatch involves keeping your morning wake time strictly fixed, seeking bright light exposure immediately upon waking, and allowing your natural sleep drive to advance your bedtime gradually over several days.

If you are unsure which of these timing issues or hidden disruptions is affecting your nights, completing the free Sleep Friction Check can help you identify where your sleep schedule and physical habits are coming into conflict.

What nightcaps and late drinks do to sleep architecture

Alcohol is a central nervous system depressant that acts on gamma-aminobutyric acid (GABA) receptors in the brain. While this enhances sedating neurochemistry and helps you drop off quickly, its metabolic effects severely degrade the structural quality of your rest over the course of the night.

In the first half of the night, alcohol suppresses REM sleep and forces the brain into an artificially heavy, sedated state that mimics deep sleep but lacks normal physiological brain wave patterns. As your liver metabolizes alcohol into acetaldehyde and acetate, blood alcohol levels drop back toward zero during the second half of the night, triggering a powerful rebound effect in your central nervous system.

This metabolic rebound causes a sharp surge in glutamatergic excitatory activity, elevating your resting heart rate, increasing body temperature, and inducing frequent micro-arousals. The rebound severely truncates REM sleep during the early morning hours, exactly when your brain naturally expects to spend the most time in REM. You may remain in bed for eight full hours after drinking, but the resulting sleep architecture is fragmented, explaining why you wake up exhausted, dehydrated, and mentally fogged.

Switching from high-proof spirits to lighter alcoholic drinks or consuming alcohol right before getting into bed does not resolve this disruption. The total amount of ethanol processed by your liver dictates the intensity of the nighttime rebound, regardless of the beverage type. To protect nighttime sleep architecture, cease alcohol intake several hours before lying down, allowing your metabolic system to clear the compound before sleep begins.

Why am I tired after enough sleep if I wake up mid-cycle

Sleep inertia is the temporary grogginess, disorientation, and cognitive slowness experienced immediately upon waking. While mild sleep inertia typically dissolves within fifteen to thirty minutes as core body temperature rises and blood flow to the prefrontal cortex increases, waking up from the wrong sleep stage can cause severe sleep inertia that lingers for hours.

Your sleep cycles repeat roughly every ninety to one hundred and twenty minutes, though individual cycle lengths vary widely across the night. If your alarm sounds while you are in the middle of stage three deep slow-wave sleep, your brain must transition instantly from high-amplitude delta waves to fast beta waves.

This abrupt transition leaves sleep-promoting chemicals, such as adenosine, bound to neuronal receptors in your brain, while core body temperature remains near its low nocturnal trough. This state leaves you feeling heavily disoriented, sluggish, and physically exhausted. Waking up from light stage 1 sleep or REM sleep creates significantly less morning grogginess than being pulled directly out of deep slow-wave sleep.

A worked example of sleep cycle timing

Consider an adult who goes to bed around 11:00 PM and sets an alarm for 6:30 AM. During the early part of the night, their sleep cycles are dominated by deep slow-wave sleep, transitioning to longer REM periods as morning approaches.

If this individual has a naturally delayed circadian rhythm, their core body temperature minimum occurs later than average, placing a final block of deep slow-wave sleep around 6:15 AM. When the alarm sounds at 6:30 AM, it forces the brain awake directly from deep sleep.

Upon waking, delta wave activity persists in the frontal regions of the brain, and adenosine clearance is incomplete. Despite getting seven and a half total hours of sleep, the person experiences intense sleep inertia, heavy limbs, and brain fog that lasts well into the late morning.

If that same person had shifted their biological clock earlier using bright morning light and consistent wake times, their final deep sleep phase would have concluded earlier in the night. The alarm at 6:30 AM would then coincide with light stage 2 sleep or REM sleep, allowing them to wake up feeling clear-headed and alert on the exact same total hours of rest.

How hidden breathing problems disrupt your sleep quality

Undiagnosed upper airway resistance and obstructive sleep apnea represent major hidden causes of unrefreshing sleep. When the airway tissues in the throat relax during sleep, they can partially or completely block the flow of air into the lungs.

When your airway narrows, your respiratory system must work significantly harder to pull air past the obstruction. This increased breathing effort creates negative intrathoracic pressure and triggers a stress response in your brain, causing a micro-arousal that restores pharyngeal muscle tone but pulls you completely out of deep sleep.

In more pronounced cases, breathing stops entirely for brief periods until rising carbon dioxide levels in the blood trigger a brainstem survival mechanism, forcing a loud gasp, snort, or sudden arousal. Because these events occur dozens or hundreds of times a night without reaching full conscious awareness, you can spend eight hours in bed completely unaware that your body was struggling for oxygen every few minutes.

Nasal dilator strips, special pillows, or mouth taping are common self-help attempts, but these measures fail when upper airway obstruction occurs in the lower throat or retroglottal space, or when severe tissue collapse is present. Relying on superficial fixes for lower airway collapse delays proper evaluation and leaves nighttime oxygen levels compromised.

If you experience loud, persistent snoring, witnessed breathing pauses, gasping, or dangerous daytime sleepiness while driving, a professional evaluation by a healthcare provider is appropriate. Learn more about evaluating airway issues by reading our guide on how to stop snoring.

The impact of late cognitive arousal versus physical fatigue

A common reason people wake up tired after eight hours in bed is the presence of high cognitive arousal late in the evening. Engaging in complex work tasks, answering high-stakes emails, or managing emotional conversations shortly before trying to sleep activates the hypothalamic-pituitary-adrenal (HPA) axis. This activation triggers the release of cortisol and plasma epinephrine, elevating resting heart rate and central nervous system alertness.

While you may feel physically exhausted from a long day, elevated cognitive arousal creates a “tired but wired” state. You may fall asleep out of sheer physical exhaustion, but your nervous system remains in a heightened state of sympathetic dominance. This prevents your brain from establishing the steady, low-frequency delta rhythms required for deep slow-wave sleep, leaving you in a extended state of shallow, fragile sleep.

Relaxation techniques like deep breathing or meditation performed right in bed often fail if you remain in a brightly lit room or keep work devices active nearby until the moment you turn off the light. The brain associates the environment with active problem-solving, maintaining central alertness despite breathwork attempts.

To resolve cognitive arousal, establish a clear boundary between daytime mental effort and nighttime rest. Complete demanding mental work several hours before bedtime, write down unresolved tasks on paper to offload mental tracking, and physically step away from work spaces to allow parasympathetic tone to rise before lying down.

Sleep debt recovery versus true sleep restoration

It is important to distinguish between accumulated chronic sleep debt and poor structural sleep restoration. Sleep debt occurs when you consistently get fewer total hours of sleep than your body requires over days or weeks. Unrefreshing sleep occurs when total hours in bed are adequate, but internal sleep architecture is disrupted.

When people attempt to clear chronic sleep debt by sleeping for ten or eleven hours on weekends, they often wake up feeling more exhausted than on weekdays. This occurs because sleeping late into the morning shifts the core body temperature phase and delays evening melatonin release. This circadian delay makes it difficult to fall asleep at a normal time on Sunday night, creating a cycle of severe sleep inertia on Monday morning.

Using weekend sleep extension as a primary strategy to solve daytime tiredness fails because it damages circadian consistency without fixing nighttime sleep architecture. Instead of extending morning sleep by multiple hours on days off, maintain a stable wake-up time throughout the week. If you need to recover from acute sleep debt, add thirty to forty-five minutes of quiet rest early in the afternoon or advance your bedtime slightly, preserving your regular morning wake time.

What daytime sleepiness means for your daily health

Feeling unrefreshed occasionally is normal, but persistent daytime sleepiness indicates that your sleep is failing to fulfill its restoration role. Daytime sleepiness manifests as an involuntary urge to nod off during quiet activities, reduced concentration, slowed reaction times, and emotional instability.

It is important to distinguish between general physical fatigue and excessive daytime sleepiness. Fatigue refers to a lack of physical energy or muscle stamina, whereas sleepiness refers to an actual physiological propensity to fall asleep during low-activity tasks. To explore what these daytime signals indicate about your underlying health, read our analysis on daytime sleepiness and what it means.

For comprehensive clinical context regarding chronic daytime sleepiness and potential primary sleep disorders, consult educational materials from the American Academy of Sleep Medicine or review resources on neurological sleep conditions through NINDS Narcolepsy.

Comparing common causes of unrefreshing sleep

To identify why you wake up tired after sleeping, compare the primary mechanisms, sleep stage impacts, and daytime effects across different common disruptions.

What to adjust in your evening routine to protect deep sleep

Protecting the deep sleep stages responsible for morning alertness requires reducing physiological stressors during the hours leading up to bed. Making targeted adjustments to your environment and habits can prevent subtle disruptions that compromise sleep quality.

• Keep your sleeping environment cool, as a falling core body temperature is a primary biological trigger for initiating deep slow-wave sleep.
• Dim overhead lighting several hours before bed to allow your pineal gland to synthesize natural sleep-signaling hormones undisturbed.
• Finish large or heavy meals several hours before lying down to prevent digestive activity from elevating your sleeping heart rate and body temperature.
• Eliminate late evening alcohol consumption to allow your autonomic nervous system to remain stable throughout the entire night.
• Minimize exposure to stressful news, work tasks, or high-intensity exercise late at night to keep sympathetic nervous system activity low before bedtime.

Failure cases for evening adjustments

Every routine adjustment has specific scenarios where it fails to produce results, requiring an alternative approach:

• Cool bedroom environment: Lowering ambient room temperature fails for individuals who experience poor distal circulation or cold hands and feet. Cold extremities cause peripheral vasoconstriction, which retains heat in the body’s core and keeps sympathetic arousal elevated. What to do instead: Wear warm socks to promote peripheral vasodilation—which releases core heat—while keeping the surrounding bedroom air cool.
• Dimming ambient lights: Reducing overhead lighting fails if you hold a bright mobile device screen close to your eyes late at night. Direct light exposure from short distances continues to stimulate intrinsically photosensitive retinal ganglion cells, suppressing natural melatonin release regardless of room lighting. What to do instead: Set devices to high warmth night modes, keep screens at a distance, or swap late screen time for printed reading or audio listening.
• Finishing meals early: Stopping food intake hours before bed fails for individuals prone to nocturnal hypoglycemia. An overly long window without food can cause overnight blood sugar drops, triggering an adrenal cortisol release that wakes the brain. What to do instead: Consume a small, balanced snack containing complex carbohydrates or protein shortly before bed if your dinner was early or light.
• Eliminating late alcohol: Stopping late alcohol fails to improve sleep if it is replaced with sugar-heavy beverages or caffeinated teas in the evening. Secondary stimulants introduce new disruptions to sleep continuity. What to do instead: Replace evening alcoholic beverages with warm, non-caffeinated herbal infusions or plain water.
• Minimizing late exercise: Moving high-intensity workouts earlier fails to improve sleep if physical activity is eliminated entirely during the day. Without sufficient daytime physical activity, homeostatic sleep pressure remains low, resulting in shallow, restless sleep. What to do instead: Perform exercise earlier in the day to build strong sleep pressure while giving your core temperature and heart rate several hours to cool down before night.

Comparing evening environmental factors and their impact on sleep continuity

Evaluating how different physical bedroom variables affect your physiology helps target adjustments effectively.

Practical adjustments to evaluate your morning sleepiness

When testing changes to improve sleep quality, evaluate one adjustment at a time over a consistent period. The table below outlines simple practical adjustments, their underlying biological mechanisms, and the timeframe required to judge their effectiveness.

How to distinguish sleep inertia from chronic fatigue

It is critical to distinguish between normal sleep inertia upon waking and persistent fatigue or excessive sleepiness that lasts throughout the day. The symptoms, duration, and underlying drivers of these conditions differ significantly.

• Duration of symptoms: Sleep inertia peaks during the first few minutes after waking and gradually fades within thirty to sixty minutes as brain wave frequency accelerates. Chronic fatigue persists continuously from morning until night, remaining largely unchanged regardless of time spent resting.
• Response to light and movement: Sleep inertia resolves rapidly when exposed to bright morning sunlight, physical movement, and cold water on the face. Chronic fatigue persists despite environmental stimulation and light exposure.
• Type of impairment: Sleep inertia presents primarily as cognitive grogginess, motor slowness, and temporary spatial disorientation. Chronic fatigue feels like deep physical exhaustion, heavy limbs, or low emotional resilience.
• Relationship to sleep duration: Sleep inertia is often intensified by waking up from a deep sleep stage mid-cycle after a long rest. Chronic fatigue reflects ongoing health demands, physiological stress, or long-term systemic recovery issues.

When to seek a professional medical evaluation

If you have consistently adjusted your sleep environment, kept a regular schedule, and allowed ample time in bed, yet still wake up exhausted for months on end, a formal medical assessment is appropriate.

A healthcare clinician can evaluate you for underlying sleep disorders, arrange for overnight sleep tracking, or check for non-sleep medical conditions that impair recovery. You can review standard diagnostic procedures and testing methodologies through the NHLBI Sleep Studies educational guide, or explore a broad index of sleeping problems on MedlinePlus: Sleep Disorders.

If your unrefreshing sleep is accompanied by persistent difficulty falling asleep or staying asleep, structured behavioural therapies are widely recognized as standard care. Cognitive Behavioral Therapy for Insomnia (CBT-I) is a structured, evidence-based approach delivered by trained clinical providers that addresses the cognitive, behavioural, and physiological patterns holding sleep problems in place.

If you want these insights turned into a structured plan built around your own nights, consider the Sleep Reset OS program ($9, one-time payment). It provides a guided approach to systematic habit adjustment without recurring subscription fees.

Frequently asked questions

Why do I wake up tired after sleeping 8 hours?

Sleeping eight hours does not guarantee high-quality rest if your sleep architecture is fragmented. Micro-arousals, hidden breathing issues, circadian timing mismatches, and late alcohol consumption can trap your brain in light stage 1 and 2 sleep, preventing the deep slow-wave and REM sleep necessary for physical and mental recovery.

Can waking up at the wrong time in my sleep cycle make me exhausted?

Yes, waking up in the middle of stage three deep slow-wave sleep triggers severe sleep inertia. When an alarm pulls you directly out of deep delta-wave sleep, your brain takes much longer to clear sleep-promoting neurotransmitters, leaving you feeling groggy, disoriented, and exhausted for hours afterward.

How do I know if I have micro-arousals during the night?

Micro-arousals last only a few seconds, so you rarely form conscious memories of them. Common daytime signs include waking up tired after sleeping enough hours, experiencing morning dry mouth, having frequent tension headaches upon waking, or feeling an intense energy slump during quiet afternoon activities.

Does drinking alcohol before bed cause unrefreshing sleep?

Alcohol disrupts sleep structure by suppressing REM sleep and inducing artificial early sedation. As your liver metabolizes the alcohol during the night, a glutamatergic rebound effect triggers sympathetic nervous system arousal, elevated heart rate, and fragmented sleep during the second half of the night.

What is the difference between feeling groggy and excessive daytime sleepiness?

Morning grogginess, or sleep inertia, is a temporary transitional state between sleep and waking that dissolves with light, movement, and rising core body temperature. Excessive daytime sleepiness is an ongoing, involuntary propensity to drop off to sleep during ordinary, passive daytime activities.

Can a cool room really improve sleep quality?

A cool bedroom helps lower your core body temperature, which is a required biological signal for entering and maintaining deep slow-wave sleep. An overly warm room prevents heat dissipation, increases body movement, and triggers frequent micro-arousals, leading to unrefreshing sleep.

When should I see a doctor about waking up tired?

You should speak with a doctor if unrefreshing sleep lasts for months, significantly interferes with your daytime functioning, or is accompanied by loud snoring, witnessed breathing pauses, gasping, morning headaches, or extreme sleepiness while operating a motor vehicle.

Why do I feel more tired on days I sleep 9 or 10 hours than when I sleep 7 hours?

Sleeping nine or ten hours often extends your rest past your normal circadian wake window. Waking up during a phase when your brain is transitioning between extended REM or late slow-wave sleep cycles increases sleep inertia. Additionally, long lie-ins lower homeostatic sleep pressure, making the following night’s sleep lighter and more fragmented.

Can late-night exercise make me wake up tired even if I fall asleep quickly?

Vigorous exercise late in the evening elevates core body temperature and releases catecholamines like adrenaline. Even if physical tiredness allows you to fall asleep rapidly, elevated core temperature and heart rate prevent your brain from establishing stable slow-wave sleep early in the night, leading to fragmented rest.

How does cognitive behavioral therapy for insomnia (CBT-I) address unrefreshing sleep?

CBT-I is a structured clinical framework delivered by trained healthcare providers that targets the psychological and behavioral drivers of poor sleep. It uses techniques such as stimulus control, sleep consolidation, and cognitive restructuring to help realign sleep timing, reduce nighttime autonomic arousal, and restore deep sleep architecture.

What to take away

• Total hours spent in bed do not equal high-quality rest if sleep architecture is disrupted.
• Micro-arousals strip away deep slow-wave sleep without leaving any conscious memory of waking up.
• Aligning your bedtime with your biological clock ensures your brain enters restorative stages smoothly.
• Waking up mid-cycle from deep sleep triggers heavy sleep inertia that lingers into the morning.
• Persistent unrefreshing sleep accompanied by snoring, gasping, or daytime sleepiness warrants a professional medical evaluation.

Sources & review

This guide is an original educational summary written from the sources below. Each URL was verified on the date recorded in our source registry.

• Sleep Apnea — National Heart, Lung, and Blood Institute (NIH)
• Sleep Disorders — MedlinePlus, U.S. National Library of Medicine
• Sleep Deprivation and Deficiency — National Heart, Lung, and Blood Institute (NIH)
• Narcolepsy — National Institute of Neurological Disorders and Stroke (NIH)

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