How Are Sleep Disorders Classified?

According to global estimates, up to 51% of adults suffer from at least one sleep disorder. Among children, sleep disorders affect roughly 20% to 30%, impacting physical health, mental well-being, productivity and quality of life. Understanding how sleep disorders are classified can help identify symptoms early, improve diagnosis and guide appropriate treatment strategies.

Sleep disorders interfere with the quantity, quality, timing, or behaviour associated with sleep. They can affect how easily a person falls asleep, how long they stay asleep, how they breathe during sleep, or how they behave while sleeping.

Sleep specialists commonly classify these disorders based on their primary symptoms and underlying mechanisms. The International Classification of Sleep Disorders (ICSD) categorises sleep disorders into several major groups.

• Insomnia disorders

• Sleep-related breathing disorders

• Central disorders of hypersomnolence

• Circadian rhythm sleep-wake disorders

• Parasomnias

• Sleep-related movement disorders

Each category affects sleep differently and requires distinct diagnostic and management approaches.

Insomnia is one of the most common sleep disorders worldwide. It involves difficulty falling asleep, staying asleep, or waking up too early despite having adequate opportunity to sleep.

• Difficulty initiating sleep

• Frequent nighttime awakenings

• Early morning awakening

• Daytime fatigue

• Poor concentration and irritability

Insomnia may be short-term, triggered by stress or life events, or chronic, lasting for three months or longer.

These disorders occur when breathing becomes abnormal during sleep. The most common type is obstructive sleep apnea (OSA), where the airway repeatedly collapses during sleep.

• Loud snoring

• Pauses in breathing during sleep

• Gasping or choking episodes

• Morning headaches

• Excessive daytime sleepiness

Untreated sleep apnea has been linked to cardiovascular disease, hypertension, diabetes and cognitive impairment.

These conditions are characterised by excessive daytime sleepiness despite obtaining sufficient sleep.

• Narcolepsy: A neurological disorder affecting the brain's ability to regulate sleep-wake cycles.

• Idiopathic hypersomnia: Persistent excessive sleepiness without a clearly identifiable cause.

Individuals may experience overwhelming daytime sleep episodes, difficulty staying awake and impaired daily functioning.

Our body follows an internal biological clock known as the circadian rhythm. When this timing system becomes disrupted, sleep disorders can develop.

• Delayed sleep-wake phase disorder

• Advanced sleep-wake phase disorder

• Shift work disorder

• Jet lag disorder

People with circadian rhythm disorders often struggle to align their sleep schedules with work, school, or social obligations.

Parasomnias involve unusual behaviours, movements, emotions, or experiences that occur during sleep or while transitioning between sleep and wakefulness.

• Sleepwalking

• Sleep talking

• Night terrors

• Nightmare disorder

• REM sleep behaviour disorder

While some parasomnias are harmless, others may increase the risk of injury and require medical evaluation.

These disorders involve repetitive movements that interfere with sleep quality.

• Restless Legs Syndrome (RLS): An uncomfortable sensation in the legs accompanied by an urge to move them.

• Periodic Limb Movement Disorder (PLMD): Repetitive limb movements during sleep.

These conditions often result in fragmented sleep and daytime fatigue.

Healthcare professionals may use several approaches to diagnose sleep disorders, including:

• Detailed sleep history

• Sleep diaries

• Physical examination

• Questionnaires and screening tools

• Polysomnography (sleep study)

• Actigraphy monitoring

An accurate diagnosis is essential because many sleep disorders share similar symptoms.

Treatment depends on the specific disorder and its severity. Common management strategies include:

• Improving sleep hygiene

• Cognitive behavioural therapy

• Stress management techniques

• Regular exercise

• Dietary modifications

• Medical devices such as CPAP for sleep apnea

• Addressing underlying medical conditions

In addition, cannabinoid-based medications are an alternative and natural therapeutic approach for certain sleep-related conditions. Emerging research suggests that specific cannabinoids may help support sleep regulation, reduce anxiety-related sleep disturbances and improve sleep quality in some individuals when taken under appropriate medical guidance. 

Understanding the classification of sleep disorders is the first step toward recognising symptoms early and seeking the right support.