Last updated on September 27th, 2017

Sleep medicine is a young and rapidly evolving science. It was only in 1953 that we started to understand sleep physiology with the discovery of REM (rapid eye movement) sleep.

So it’s not surprising that the task of categorizing sleep disorders was only undertaken a few decades ago. And it’s far from a finished project. The nosology (the way disorders are classified) of sleep medicine is far from fixed. Conditions such as sleep apnea require a physiological approach to diagnosis and treatment, whilst other disorders may require the expertise of mental health professionals.

It’s unlikely we’ll arrive at a ‘unified theory’ of sleep medicine any time soon, but for now, the standard tool used by the majority of health professionals dealing with sleep disorders is the International Classification of Sleep Disorders (ICSD).

How do you define a sleep disorder?

The first attempt to classify sleep disorders came in 1979.  The Diagnostic Classification of Sleep and Arousal Disorders, published in the newly formed journal, Sleep, was largely organized into symptomatic categories ie (insomnia, hypersomnia, and abnormal events occurring whilst sleep). However, it was difficult to make a diagnosis based on pathophysiology (quantifiable measurement) because most of the causes of sleep disorders were unknown at the time.

By 1990, knowledge had progressed sufficiently to warrant a new classification. The International Classification of Sleep Disorders (ICSD) was published by the major international sleep societies at the time, a group comprising of the American Sleep Disorders Association (ASDA), European Sleep Research Society, the Japanese Society of Sleep Research, and the Latin American Sleep Society.  The ICSD comprised 84 separate disorders based on pathophysiological concepts. In 2002, the American Academy of Sleep Medicine set up a committee to further revise the classification resulting in the current classification, the ICSD-2.

ICSD – an international standard

The ICSD-2 was published with the goal of standardizing definitions of sleep disorders and creating a systematic approach to diagnosis. It is widely used by clinicians and researchers worldwide, improving research efforts throughout the international community by adhering to a recognised set standards.The ICSD-2 outlines the  following goals:

  1. To describe all currently recognised sleep and arousal disorders, and to base the description on scientific and clinical evidence.
  2. To present the sleep and arousal disorders in an overall structure that is rational and scientifically valid
  3. To render the sleep and arousal disorders as compatible with ICD-9 and ICD-10 as possible
As a result the ISCD-2 organises sleep disorders into the following eight categories.
  1. Insomnias
  2. Sleep Related Breathing Disorders
  3. Hypersomnias of Central Origin Not Due to a Circadian Rhythm Sleep Disorder, Sleep Related Breathing Disorder or Other Cause of Disturbed Nocturnal Sleep
  4. Circadian Rhythm Sleep Disorders
  5. Parasomnias
  6. Sleep Related Movement Disorders
  7. Isolated Symptoms, Apparent Normal Variants, and Unresolved Issues
  8. Other Sleep Disorders

Are these definitions likely to change?

The science of sleep medicine is still an emerging field and new discoveries are being made all the time. So whilst the ICSD-2 is the most up to date classification of sleep disorders in use today, there will no doubt be more revisions as knowledge progresses over the coming years. Sleep medicine practitioners will have to be flexible in their approach and adapt the way they categorise, diagnose and treat sleep disorders.

CATEGORY/SUB-CATEGORYSLEEP DISORDERALTERNATIVE NAMES
INSOMNIA
Adjustment InsomniaAcute insomnia, short term insomnia
Psychophysiological Insomnia
Paradoxical InsomniaSleep state misperception
Idiopathic InsomniaPrimary insomnia
Insomnia Due to Mental Disorder
Inadequate Sleep Hygiene
Behavioral Insomnia of Childhood
Insomnia Due to Drug or Substance
Insomnia Due to Medical Condition
Insomnia Not Due to Substance or Known Physiological Condition
Physiological (Organic) Insomnia, Unspecified
SLEEP RELATED BREATHING DISORDERS
Central Sleep Apnea Syndromes
Primary Central Sleep Apnea
Central Sleep Apnea Due to Cheyne Stokes Breathing Pattern
Central Sleep Apnea Due to High-Altitude Periodic Breathing
Central Sleep Apnea Due to Medical Condition Not Cheyne Stokes
Central Sleep Apnea Due to Drug or Substance
Primary Sleep Apnea of Infancy (Formerly Primary Sleep Apnea of Newborn)
Obstructive Sleep Apnea Syndromes
Obstructive Sleep Apnea, AdultOSA, sleep apnoea
Obstructive Sleep Apnoea, PediatricChild sleep apnea
Sleep Related Hypoventilation/Hypoxemic Syndromes
Sleep Related Nonobstructive Alveolar Hypoventilation, Idiopathic
Congenital Central Alveolar Hypoventilation Syndrome
Sleep Related Hypoventilation/Hypoxemia Due to Medical Condition
Sleep Related Hypoventilation/Hypoxemia Due to Pulmonary Parenchymal or Vascular Pathology
Sleep Related Hypoventilation/Hypoxemia Due to Lower Airways Obstruction
Sleep Related Hypoventilation/Hypoxemia Due to Neuromuscular and Chest Wall Disorders
Other Sleep Related Breathing Disorder
Sleep Apnea/Sleep Related Breathing Disorder, Unspecified
HYPERSOMNIAS OF CENTRAL ORIGIN
Narcolepsy With Cataplexy
Narcolepsy Without Cataplexy
Narcolepsy Due to Medical Condition
Narcolepsy, Unspecified
Idiopathic Hypersomnia With Long Sleep TimePrimary hypersomnia
Idiopathic Hypersomnia Without Long Sleep TimePrimary hypersomnia
Behaviorally Induced Insufficient Sleep Syndrome
Hypersomnia Due to Medical Condition
Hypersomnia Due to Drug or Substance
Hypersomnia Not Due to Substance or Known Physiological ConditionNonorganic hypersomnia, NOS
Physiological (Organic) Hypersomnia, UnspecifiedOrganic hypersomnia, NOS
Recurrent HypersomniaRecurrent Hypersomnia
Kleine-Levin SyndromeSleeping beauty syndrome
Menstrual-Related Hypersomnia
CIRCADIAN RHYTHM SLEEP DISORDERS
Circadian Rhythm Sleep Disorder, Delayed Sleep Phase TypeDelayed sleep phase disorder, delayed sleep phase syndrome
Circadian Rhythm Sleep Disorder, Advanced Sleep Phase TypeAdvanced sleep phase disorder
Circadian Rhythm Sleep Disorder, Irregular Sleep-Wake TypeIrregular sleep-wake rhythm
Circadian Rhythm Sleep Disorder, Free-Running TypeNonentrained type
Circadian Rhythm Sleep Disorder, Jet Lag TypeJet lag
Circadian Rhythm Sleep Disorder, Shift Work TypeShift work disorder
Circadian Rhythm Sleep Disorder Due to Medical Condition
Other Circadian Rhythm Sleep Disorder Circadian rhythm disorder, NOS
Other Circadian Rhythm Sleep Disorder Due to Drug or Substance
PARASOMNIAS
Disorders of arousal (from non-REM sleep)
Confusional arousals
SleepwalkingSomnambulism
Sleep terrorsNight Terrors
Parasomnias usually associated with REM sleep
REM sleep behavior disorder (including parasomnia overlap disorder and status dissociatus)REM sleep disorder, RBD
Recurrent isolated sleep paralysisSleep paralysis
Nightmare disorderNightmares
Other Parasomnias
Sleep Related Dissociative Disorders
Sleep EnuresisBedwetting , nocturnal enuresis
Sleep Related GroaningCatathrenia
Exploding Head Syndrome
Sleep Related Hallucinations
Sleep Related Eating DisordersSRED
Parasomnia, Unspecified
Parasomnia Due to Drug or Substance
Parasomnia Due to Medical Condition
SLEEP RELATED MOVEMENT DISORDERS
Restless Legs Syndrome
Periodic Limb Movement Disorder
Sleep Related Leg Cramps
Sleep Related BruxismTeeth grinding
Sleep Related Rhythmic Movement Disorder
Sleep Related Movement Disorder, Unspecified
Sleep Related Movement Disorder Due to Drug or Substance
Sleep Related Movement Disorder Due to Medical Condition
ISOLATED SYMPTOMS, APPARENTLY NORMAL VARIANTS AND UNRESOLVED ISSUES
Long Sleeper
Short Sleeper
Snoring
Sleep Talking
Sleep StartsHypnic jerks
Benign Sleep Myoclonus of Infancy
Hypnagogic Foot Tremor and Alternating Leg Muscle Activation During Sleep
Propriospinal Myoclonus at Sleep Onset
Excessive Fragmentary Myoclonus
OTHER SLEEP DISORDERS
Other Physiological (Organic) Sleep Disorder
Other Sleep Disorder Not Due to Substance or Known
Physiological Condition
Environmental Sleep Disorder
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Jeff Mann
Jeff Mann is the founder and editor of Sleep Junkies. Get in touch at jeff [at]sleep junkies[dot]com
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