The American Academy of Sleep Medicine International Classification of Sleep Disorders (ICSD) is the key reference work for diagnosing sleep problems, including sleep-related medical and neurological conditions. Based on ICSD diagnostic criteria, sleep disorders are grouped into six major categories:

1. Insomnia Disorders
   • Defined as a persistent difficulty with sleep initiation, duration or consolidation that occurs despite adequate opportunity and circumstances for sleep and results in concern, dissatisfaction or perceived daytime impairment, such as fatigue, decreased mood or irritability, general malaise, or cognitive impairment. Difficulties initiating or maintaining sleep or a non-restorative rest despite adequate sleep opportunity and circumstances are most common.
2. Sleep-Related Breathing Disorders
   • Characterized by disruptions in normal breathing patterns during sleep. This category includes conditions such as obstructive sleep apnea, central sleep apnea, and sleep-related hypoventilation. Sleep disordered breathing is associated with health risks such as heart disease, hypertension and strokes.
3. Central Disorders of Hypersomnolence
   • Caused by dysfunction in the central nervous system characterized by excessive daytime sleepiness despite normal or prolonged sleep time and not caused by a circadian rhythm sleep-wake disorder or another untreated sleep condition such as sleep apnea. Examples are narcolepsy and idiopathic hypersomnia.
4. Circadian Rhythm Sleep-Wake Disorders
   • Characterized by a disruption in the timing of the sleep-wake cycle. Symptoms can include difficulties falling asleep, staying asleep, or waking up at desired times which can lead to excessive daytime sleepiness, insomnia, or other sleep-related issues.
5. Parasomnias
   • Parasomnias are undesirable physical events or experiences that occur during entry into sleep, within sleep, during arousal from sleep or during sleep-wake transitions. Examples are acting out of dreams (sometimes violently), sleep walking and nightmares
6. Sleep-Related Movement Disorders
   • Characterized by repetitive, stereotyped movements or behaviors that disrupt sleep and can lead to excessive daytime sleepiness and impaired functioning. These include rhythmic movements, periodic limb movements, restless legs syndrome, bruxism (teeth grinding), and more.