Advanced Sleep-Wake Phase Disorder: Early Sleep and Early Waking
Author: Angela Bogdanova · Published: October 10, 2026 · Editorial Policy
Research cluster: Sleep, Insomnia & Circadian Psychology · Written by Artificial Sapiens
Advanced sleep-wake phase disorder (ASWPD) is a circadian rhythm sleep-wake disorder in which the main period of sleep occurs consistently earlier than a person wants or needs. Someone may become overwhelmingly sleepy in the early evening and awaken for the day in the very early morning, despite wanting to stay awake for evening activities and sleep later. The central clinical issue is a persistent mismatch between the timing of the internal body clock and the timing of ordinary obligations, accompanied by distress or functional impairment. The National Heart, Lung, and Blood Institute (NHLBI) recognizes ASWPD as a distinct circadian disorder, and the American Academy of Sleep Medicine (AASM) classifies circadian rhythm sleep-wake disorders within the ICSD-3-TR.
The apparent paradox is that a person with ASWPD may sleep reasonably well when allowed to follow an unusually early schedule. The problem becomes apparent when the person tries to match a later social schedule. Staying awake until a desired bedtime may shorten sleep because their internal wake time remains unusually early. This pattern is different from waking early because of chronic insomnia, depression, insufficient sleep, an alarm, or a naturally preferred morning routine. The distinction determines whether circadian treatment is appropriate. The AASM clinical guideline identifies evening light therapy as a conditional option for adults, while acknowledging very low certainty and limited treatment studies.
What advanced sleep-wake phase disorder means
The term advanced refers to clock timing: an advanced circadian phase places biological night earlier relative to local time. It does not mean that the person sleeps more deeply, requires less sleep, or has a more developed body clock. Sleepiness, body temperature rhythms, melatonin timing, and the preferred sleep period may all occur earlier than usual. The person commonly describes two linked problems: difficulty remaining awake until the desired evening bedtime and difficulty remaining asleep until the desired morning wake time. Both sides of this pattern matter. AASM's evidence review describes these characteristic complaints.
For illustration, a person may feel compelled to fall asleep around 7:30 p.m. and wake naturally near 3:30 a.m. Those times are examples, not diagnostic thresholds. Another person may sleep from 8:30 p.m. to 4:30 a.m. and have no impairment because the schedule suits their life. Clinical significance depends on persistence, the degree of advancement relative to desired timing, adequate sleep on the preferred schedule, competing causes, and the consequences for daily life.
The disorder is less common than delayed sleep-wake phase disorder. Estimates vary greatly with case definitions and populations, and a recent scholarly review reports prevalence estimates ranging from 0% to approximately 0.33%. Such figures deserve caution because mild early chronotypes, age-related changes, and clinically impairing ASWPD are not always separated consistently. The 2025 Oxford review of advanced and delayed phase disorders emphasizes that ASWPD is relatively rare and infrequently presents for treatment.
Symptoms and the everyday pattern
Evening sleepiness that comes earlier than desired
People may become intensely sleepy during dinner, family time, meetings, performances, social events, or the later part of a work shift. Some struggle to remain awake despite genuine motivation. This is different from choosing an early bedtime out of preference or routine. Someone who repeatedly forces themselves to stay up may find that the following morning still begins exceptionally early, creating a period of restricted sleep.
Very early final awakening
Awakening may occur several hours before the desired time, often with a feeling that the night's main sleep episode is complete. There may be little ability to return to sleep, particularly when the person has already slept through their biological night. Early awakening can resemble sleep-maintenance insomnia, so clinicians ask when sleep began, whether sleep is restorative on unrestricted days, and whether the timing pattern remains stable.
Daytime consequences
The most important consequences arise when the schedule collides with responsibilities. Evening driving, caregiving, relationships, employment, and social engagement can become difficult. Repeatedly delaying bedtime without shifting the underlying circadian phase can lead to shorter sleep, fatigue, irritability, impaired attention, and sleepiness at unsafe times. These consequences reflect both timing mismatch and accumulated sleep loss; a pattern of early sleep alone is insufficient to explain them. The NHLBI overview of circadian disorders explains the role of mismatch and functional impairment.
Does ASWPD affect sleep quality or just timing?
Many affected people report a reasonably consolidated, sufficiently long sleep episode when they follow their preferred early schedule. Their chief difficulty is its placement within the 24-hour day. Others have a coexisting problem such as insomnia, obstructive sleep apnea, pain, nocturia, or medication effects, and therefore have both circadian mistiming and genuinely disrupted sleep. A successful evaluation looks for both rather than assuming that early wake time explains every complaint.
The biological clock: why sleep moves earlier
The brain's suprachiasmatic nucleus coordinates near-24-hour rhythms with external timing cues, especially the daily cycle of light and darkness. Sleep timing also depends on homeostatic sleep pressure, behavior, social routines, and the opportunity to sleep. A person's habitual sleep period is the combined result of these interacting systems. A stable early sleep phase may reflect an earlier circadian signal, heightened morning preference, and the way environmental cues reinforce the schedule. The NHLBI circadian explanation and the 2025 review of emerging circadian assessments describe these biological and behavioral dimensions.
Light exposure can change circadian phase, but its effect depends on biological timing. Light in the late biological day or early biological night tends to delay circadian rhythms, shifting sleep and wake propensity later; appropriately timed light after the biological night tends to advance them. An ordinary wall clock is an imperfect substitute for knowing a person's biological phase. Thus a light intervention intended to delay sleep in ASWPD differs from the morning-light strategies used for delayed sleep-wake phase disorder. The NHLBI light-treatment overview explains the direction of these effects.
Age, morningness, and individual variation
On average, circadian timing tends to become earlier with age, although individual trajectories vary. Being an older adult, an early riser, or someone who enjoys mornings is not itself evidence of disease. ASWPD is diagnosed through an impairing and persistent mismatch relative to the sleep timing a person needs or desires, together with an appropriate clinical evaluation. Older adults also experience sleep fragmentation for a range of reasons, making it especially important to separate circadian phase from insufficient or interrupted sleep. A review of circadian disorders in older adults addresses this differential.
Familial advanced sleep phase and clock genes
A minority of individuals have a familial form with multiple affected relatives, sometimes across generations. Landmark studies identified particular variants affecting clock-related pathways, including PER2 and casein kinase I delta, showing that inherited changes in circadian regulation can produce very early sleep timing. The original PER2 family study and a later casein kinase I delta study established important mechanistic evidence. These discoveries do not mean that most early risers have a single-gene disorder or that genetic testing is a routine requirement for diagnosis. Family history is clinically informative, while testing is considered only in selected contexts.
Diagnostic criteria: when early timing becomes a disorder
The ICSD-3-TR framework and published interpretations of the criteria describe a specific clinical pattern. The details are assessed by a clinician rather than by a bedtime quiz.
First, the major sleep episode is persistently earlier than the person's desired or required schedule. This is reflected in difficulty remaining awake to the desired bedtime and difficulty maintaining sleep until the desired wake time. Second, the symptoms have been present for at least three months. Third, a sleep log and, when available, actigraphy document the habitual timing across at least seven days; clinicians often prefer longer records that include both workdays and free days. Fourth, when the individual can follow their preferred early hours without external restrictions, sleep duration and quality are generally appropriate for that individual. Finally, another sleep disorder, medical or neurological illness, psychiatric condition, medication, or substance effect must not better explain the disturbance. See the AASM circadian practice guideline and a clinical review summarizing ASWPD criteria.
Clinically significant distress or impairment remains central. A person who wakes at 4 a.m., feels rested, and finds that schedule useful may simply have an early chronotype. A person whose involuntary early sleepiness repeatedly interferes with employment and relationships warrants a more detailed evaluation. No particular bedtime or wake time proves ASWPD without this context.
An illustrative sleep pattern
Imagine someone with a stable pattern of becoming sleepy at 7 p.m., sleeping from 8 p.m. until 4 a.m., and feeling rested when allowed to keep those hours. On evenings when the person remains awake until 11 p.m., the next morning still begins around 4 a.m. They then accumulate sleep loss and struggle during evening obligations. A clinician might consider ASWPD if this pattern persists, causes impairment, and alternative causes have been evaluated.
Now imagine someone who falls asleep at midnight, wakes at 4 a.m. with anxiety and low mood, and cannot return to sleep. This is not the same pattern: the first question is why sleep was prematurely terminated, not whether the person's entire biological night has advanced. Likewise, a person who voluntarily sleeps at 8 p.m. and rises at 4 a.m. without distress is not necessarily experiencing a disorder.
How clinicians evaluate suspected ASWPD
Clinical interview and a sleep history
Evaluation begins with an account of habitual bedtime, actual sleep onset, awakenings, final rising time, desired hours, evening sleepiness, free-day sleep, naps, work requirements, environmental light, caffeine and alcohol, medicines, medical conditions, and mental health symptoms. Clinicians may ask how the pattern developed, whether it has been stable for months, whether relatives share it, and whether the person feels better on a schedule without externally imposed timing.
A key diagnostic question is what happens when social constraints are removed. In a circadian phase disorder, sleep can be more satisfactory at the person's spontaneous biological times. However, that observation alone does not eliminate coexisting illness, and a few comfortable free days cannot prove a chronic rhythm disorder.
Sleep diary: what it can and cannot show
A structured sleep diary records attempted bedtime, estimated sleep onset, nighttime awakenings, final waking, rising, naps, and relevant daily exposures or obligations. At least seven days of records are used in the published diagnostic framework, and 14 days may provide a clearer picture of workdays and weekends. A diary makes the pattern and its regularity visible, but it measures reported sleep rather than directly reading the body's circadian clock. The AASM guideline and the 2025 circadian assessment review discuss this approach.
Actigraphy and consumer sleep trackers
Clinical actigraphy typically uses a validated movement-based device worn across multiple days to estimate rest-activity and sleep timing. The 2018 AASM clinical practice guideline conditionally supports actigraphy for adults and children with suspected circadian rhythm sleep-wake disorders. Its special value is documenting patterns over time without assuming that one laboratory night represents habitual sleep.
An ordinary consumer watch or phone app may help someone notice a recurring schedule but cannot establish a circadian diagnosis, determine biological phase precisely, or rule out disorders such as sleep apnea. Sleep stage estimates generated by commercial algorithms should not be confused with clinical polysomnography. The AASM's actigraphy guideline addressed clinical-grade devices; the 2025 methodological review describes continuing uncertainties around consumer wearables and circadian assessment.
Melatonin phase markers and sleep studies
Specialist centers sometimes assess dim-light melatonin onset (DLMO), a physiological marker of circadian phase. Sampling requires carefully controlled timing and lighting, and access may be limited. Such testing can inform difficult cases or precise treatment planning, but the standard diagnostic framework does not routinely require it. New home-based markers and prediction tools remain under development rather than established replacements for comprehensive assessment. See the 2025 assessment review.
A routine overnight sleep study is not generally required solely to diagnose ASWPD. Polysomnography may be appropriate when symptoms suggest a different or additional disorder, such as obstructive sleep apnea, unusual sleep behaviors, or unexplained severe sleepiness. The decision depends on the broader clinical picture, not on an early wake time alone.
ASWPD versus other reasons for waking early
ASWPD versus early morning awakening insomnia
Insomnia describes difficulty initiating or maintaining sleep or awakening before the desired time, combined with relevant distress or impairment despite adequate sleep opportunity. Early morning awakening is a symptom that can appear in many conditions. In ASWPD, the entire habitual sleep window is shifted earlier, and sleep may be adequate when its timing is unrestricted. In chronic insomnia, sleep may remain disturbed even when the person chooses an appropriate bedtime and has sufficient opportunity. The two conditions can coexist. The AASM behavioral insomnia guideline supports multicomponent cognitive behavioral therapy for chronic insomnia (CBT-I), an intervention targeting insomnia mechanisms rather than serving as a universal method for delaying circadian phase.
ASWPD versus normal morning chronotype
Chronotype describes individual preference or tendency toward earlier or later activity and sleep. Morning-oriented people may naturally rise early, function well, and enjoy their preferred schedule. A chronotype becomes relevant to clinical care when an unusually advanced sleep schedule produces a sustained conflict with needed timing, notable impairment, and a pattern satisfying disorder criteria. Social convention alone does not transform a healthy preference into pathology.
ASWPD versus delayed sleep-wake phase disorder
Delayed sleep-wake phase disorder involves the opposite timing direction: difficulty falling asleep until very late and difficulty awakening at socially required morning hours. ASWPD involves disproportionately early evening sleepiness and early morning awakening. The difference is consequential because phase-shifting light strategies differ. For the opposite pattern, see Delayed Sleep-Wake Phase Disorder: Symptoms and Treatment.
ASWPD versus depression, anxiety, and stress-related sleep disruption
Early awakening may occur with depression, stress, anxiety, grief, pain, or sleep-related worry. The presence of a mental health condition neither confirms nor excludes ASWPD. Clinicians examine mood symptoms, patterns of daytime distress, when sleepiness begins, and whether the whole sleep period moves earlier. Published English Hub resources on depression-related sleep problems and the anxiety-sleep cycle address those different search intents.
ASWPD versus insufficient sleep, aging, and medical causes
An individual rising early for work may simply be chronically short of sleep. In older adults, earlier preferred sleep timing can coexist with pain, nighttime urination, medications, breathing disorders, or sleep fragmentation. Daytime fatigue and falling asleep in the evening also occur after accumulated sleep debt. These alternatives warrant review before a stable circadian disorder is assigned. A diagnosis that explains sleep timing should not distract from a treatable medical cause of nighttime awakenings.
ASWPD versus other circadian rhythm sleep-wake disorders
Non-24-hour sleep-wake rhythm disorder generally produces a sleep schedule that drifts progressively through clock time rather than remaining stably advanced. Irregular sleep-wake rhythm disorder features fragmented sleep distributed across the 24-hour day with an attenuated consolidated major sleep episode. Shift work disorder concerns schedules that overlap habitual biological sleep periods, while jet lag follows crossing time zones. The NHLBI classification separates these patterns. Consistency, trajectory, environment, and context are decisive.
Treatment: aligning the biological night with a livable schedule
Treatment is considered when symptoms interfere with the person's life and when the desired timing change is realistic. The goal is a sleep period that fits important commitments while preserving adequate duration, safety, and individual health. Management may combine carefully timed light, consistent scheduling, environmental changes, treatment of comorbid illness, and monitoring of functional improvement. Treatment depends on whether the person has ASWPD, a milder morning chronotype, insomnia, or multiple conditions.
Evening bright light: the principal guideline-supported option
The 2015 AASM evidence-based guideline suggests evening light therapy for adults with ASWPD rather than no treatment. The recommendation is weak or conditional, and the supporting evidence is graded very low: available trials are small, treatment methods differ, and some participants in older studies did not meet clearly established diagnostic criteria. This is a reasonable clinical option, not a treatment with a guaranteed response.
Light is timed to help shift the circadian clock later. A clinician may consider bright light in the late afternoon or evening, taking account of the individual's usual sleep hours, retinal or ocular health, medications, mood history, and response. The NHLBI treatment guide specifically distinguishes later-day light for shifting sleep later from morning light used to shift sleep earlier. Simply exposing someone to a bright lamp at any arbitrary clock hour may have the wrong effect. The intensity, duration, and wavelength should be selected with appropriate clinical guidance; a generic internet schedule is unsuitable for all patients.
Safety and tolerability of light treatment
Possible adverse effects include eye strain, headache, migraine, nausea, agitation, or sleep disruption if the timing is inappropriate. People with significant eye disease or taking photosensitizing medication should discuss light treatment with a clinician. Anyone with bipolar disorder or a history of mania or hypomania warrants particular care because changes in light exposure and sleep timing can affect mood stability. The NHLBI guidance describes general risks and recommends medical advice for eye conditions or light-sensitive medication. For the separate mood-disorder context, see Bipolar Disorder and Sleep.
An effective plan monitors both the sleep phase and the total amount of sleep. If a person delays bedtime substantially while their wake time stays fixed, treatment can initially worsen sleep restriction or daytime sleepiness. Anyone performing hazardous work or driving while sleepy should prioritize immediate safety and professional evaluation rather than forcing an experimental schedule.
Sleep scheduling and everyday routines
A stable wake time, predictable sleep opportunity, daytime activity, and a practical approach to light exposure can support an individualized plan. Where life circumstances permit, adjusting social commitments to the person's stable early chronotype may be more appropriate than attempting substantial biological phase shifts. Sleep diaries help judge whether a timing change is actually improving evening functioning without causing sleep loss.
It is important to distinguish a schedule-supporting recommendation from a proven cure. The AASM's ASWPD guideline did not find adequate evidence for a standalone prescribed sleep-wake scheduling recommendation. The same lack of sufficient ASWPD-specific trials applies to timed exercise and strategic light avoidance as distinct treatments. General sleep health measures remain useful, but they should not be presented as established phase-shifting therapies for ASWPD.
What about melatonin?
Melatonin is often discussed as if it were a universal solution for all body-clock problems. Its effect depends heavily on when it is taken relative to the person's biological phase. Crucially, the AASM 2015 guideline found insufficient evidence to recommend melatonin or melatonin agonists as an ASWPD treatment. Evidence and recommendations for delayed sleep-wake phase disorder or non-24-hour disorder should not be transferred automatically to ASWPD.
The NHLBI treatment resource discusses variable supplement content, adverse effects, and medication interactions. People should not start high-dose or unusually timed melatonin regimens based solely on online phase-response diagrams. Clinical assessment is especially important with pregnancy, interacting medicines, complex health conditions, or mood disorders.
Sleeping pills and stimulant medications
Sedatives might change perceived sleepiness, and stimulants might temporarily affect alertness, but neither automatically corrects an advanced circadian clock. The AASM ASWPD guideline did not establish evidence sufficient to recommend sleep-promoting drugs or wake-promoting drugs as disorder-specific phase treatment. Medication decisions require individualized consideration of indications, risks, age, other diagnoses, and interactions. Abruptly changing prescribed medication or using substances to override sleepiness can introduce new harms.
When CBT-I helps, and when a different treatment is needed
If someone has chronic insomnia in addition to an advanced phase, a clinician may recommend CBT-I for the insomnia component. The AASM CBT-I guideline supports multicomponent CBT-I for adult chronic insomnia and does not recommend sleep hygiene alone as an adequate standalone treatment. However, restrictive behavioral insomnia protocols should not be casually used to force a much later bedtime in someone whose biological wake time remains early. Coordinating the circadian and insomnia components is important to avoid unnecessary sleep loss.
Treatment decisions in older adults and families
ASWPD is often discussed in relation to aging because many people experience a gradual advance in preferred sleep timing over the lifespan. Clinicians should distinguish this expected variability from a disorder that impairs quality of life. They should also examine medication burden, vision changes, exposure to daylight, social isolation, cognitive symptoms, chronic disease, and sleep-related breathing symptoms. The older-adult circadian review describes why several factors may shape sleep-wake timing in this group.
In a family with unusually early sleepers across generations, clinicians may ask whether the pattern has been present since youth and whether affected relatives feel rested on spontaneous schedules. Such a pattern can inform consideration of familial advanced sleep phase. Genetic discoveries provide an explanation for certain families, but they do not determine the diagnosis for every person with early morning preference.
Children and adolescents with unusual sleep patterns require age-appropriate evaluation. The research base and treatment recommendations for adults should not automatically be applied to children. School schedules, developmental sleep needs, neurodevelopmental conditions, medicines, and family routines may all change the interpretation.
What you can record before a sleep appointment
A short, structured record can make a consultation more productive. Over one to two weeks, note when you first become sleepy, when you get into bed, your estimated sleep onset, major awakenings, final waking, when you rise, naps, and what happens on work-free days. Also note late-evening obligations, relevant exposure to bright light, medicines, caffeine, alcohol, and whether you felt alert or impaired at key times. This is preparation for clinical assessment, not a home diagnostic protocol. If a professional recommends actigraphy, keep the diary alongside it.
It can also help to answer a few questions in ordinary language: Have you consistently wanted to sleep later than your body allows? Do you feel better when following your early natural schedule? Have the symptoms lasted three months or more? Did the pattern exist before a recent illness or medication change? Is evening sleepiness preventing important activities? These observations help distinguish a clinical mismatch from a benign early chronotype.
For someone whose early hours are satisfactory and whose daytime life functions well, treatment may be unnecessary. If the person wants to shift sleep, the goal should be negotiated rather than imposed on the assumption that a conventional bedtime is inherently healthier.
When to see a sleep specialist
Professional evaluation is appropriate when the early sleep pattern repeatedly disrupts work, caregiving, social relationships, or emotional well-being; when it is persistent and difficult to change; or when efforts to delay bedtime lead to short sleep and dangerous sleepiness. A sleep medicine clinician can assess circadian timing, coexisting insomnia, and medical causes and can decide whether supervised light treatment or specialized phase assessment is appropriate.
Seek prompt medical attention for concerning symptoms that may indicate another disorder, such as loud snoring with witnessed breathing pauses, episodes of falling asleep unintentionally in dangerous situations, rapidly worsening confusion, significant mood changes, or possible mania. If driving or operating machinery becomes unsafe because of sleepiness, stop the hazardous activity and obtain appropriate help. Persistent early awakening with severe depressive symptoms also merits direct clinical attention. Those signs require an evaluation broader than clock timing.
What the evidence establishes—and what remains uncertain
The diagnostic pattern of ASWPD is well recognized in sleep-medicine classification. The value of longitudinal sleep history, sleep logs, and carefully selected actigraphy is supported by professional guidance. Human family studies demonstrate that clock-gene variants can cause advanced timing in selected kindreds. The AASM's evening-light recommendation is a conditional clinical recommendation supported by very low-quality evidence, and it is appropriate to describe its strength exactly. These are different forms and strengths of evidence.
Research gaps remain substantial. ASWPD-specific randomized trials are scarce, optimal light schedules are not firmly established, long-term durability is uncertain, and real-world responses may depend on endogenous circadian phase, visual sensitivity, work obligations, and the presence of other sleep disorders. Biomarker tests and consumer-derived timing algorithms are promising research directions but are not routine, independently validated substitutes for a clinical evaluation. The 2025 review of circadian assessment innovations documents both methodological progress and remaining barriers.
Frequently asked questions
Is advanced sleep-wake phase disorder the same as waking up at 4 a.m.?
No. An early wake time is one observation. ASWPD involves a persistently early main sleep episode, undesired early evening sleepiness, early morning awakening, and meaningful difficulty matching needed or desired sleep hours. Clinicians also assess how well someone sleeps on their natural schedule and whether competing explanations fit better.
Can I have ASWPD if I still get seven or eight hours of sleep?
Yes. The clinical problem may be the timing rather than a short total duration. Someone may sleep adequately from 8 p.m. to 4 a.m., yet have significant impairment from unavoidable evening commitments. Adequate sleep alone does not confirm or rule out the condition.
Is ASWPD a form of insomnia?
ASWPD is classified as a circadian rhythm sleep-wake disorder. It can create an insomnia-like complaint of waking too early, especially when someone tries to sleep at later hours. Coexisting insomnia remains possible and needs separate assessment.
Is being a morning person a sleep disorder?
No. An early chronotype can be a healthy individual difference. ASWPD requires a clinically consequential mismatch and a characteristic persistent pattern after evaluation of alternatives.
Does ASWPD only affect older people?
No. It may be more often recognized among older adults, but familial forms can appear much earlier. Age influences circadian timing without determining whether a person has the disorder.
Can evening light help me sleep later?
Clinically timed evening light is a guideline-supported option for adults with ASWPD, but the recommendation is conditional and based on very low-certainty evidence. Timing and safety assessment matter, and indiscriminate bright light may be counterproductive.
Should I take melatonin to correct an advanced sleep phase?
There is insufficient ASWPD-specific evidence for the AASM to recommend melatonin as a disorder treatment. Melatonin is strongly timing-dependent, and clinical guidance is preferable to experimenting with supplements.
Do I need a sleep study or genetic test?
Neither is routinely necessary for a straightforward timing presentation. Clinicians often start with history, sleep diaries, and sometimes actigraphy. A sleep study or specialized phase testing may be indicated by other symptoms; genetic evaluation applies to selected familial contexts.
Can ASWPD go away if I simply stay awake later?
Forcing a later bedtime without shifting the body clock can reduce sleep because spontaneous wake time may remain early. Sustainable management considers circadian timing, sufficient sleep opportunity, and underlying conditions rather than relying on willpower.
How long must the pattern last before clinicians consider ASWPD?
The published diagnostic framework calls for symptoms lasting at least three months, with a documented advanced sleep-wake pattern over at least seven days. This is a diagnostic component, not an instruction to postpone evaluation when sleepiness creates immediate safety problems.
Related Articles
Delayed Sleep-Wake Phase Disorder: Symptoms and Treatment explains the opposite circadian timing problem and the distinct approach to appropriately timed light and melatonin.
Insomnia: Symptoms, Causes, Diagnosis, and Treatment covers sleep complaints and treatment when sleep itself is disrupted beyond the timing mismatch.
Depression and Sleep: Insomnia, Oversleeping, and Treatment examines a separate cause of early awakening and altered sleep.
Bipolar Disorder and Sleep: Mood Episodes, Circadian Rhythms, and Prevention discusses mood-stability considerations relevant to changes in sleep timing and bright-light exposure.
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