Catathrenia is a rapid eye movement sleep parasomnia consisting of end-inspiratory apnea (breath holding) and expiratory groaning during sleep. Catathrenia is distinct from both somniloquy and obstructive sleep apnea. The sound is produced during exhalation as opposed to snoring which occurs during inhalation. It is usually not noticed by the person producing the sound but can be extremely disturbing to sleep partners. Bed partners generally report hearing the person take a deep breath, hold it, then slowly exhale; often with a high-pitched squeak or groaning sound.

Catathrenia typically, sometimes even exclusively, occurs during REM sleep, although it may also occur to a lesser degree during NREM sleep. Catathrenia begins with a deep inspiration. The sufferer holds her or his breath against a closed glottis, similar to the Valsalva maneuver. After a period of time and some blood oxygen desaturation, there is an arousal, followed by expiration. Expiration can be slow and accompanied by sound caused by vibration of the vocal cords or a simple rapid exhalation with no sound.

There is debate about whether the cause is physical or neurological, a question that requires further study. While some speculate about a direct correlation to high anxiety and stress or the concept that catathrenia is purely psychological, there is only anecdotal evidence of either proposed cause.

Catathrenia has been defined as a parasomnia in the International Classification of Sleep Disorders Diagnostic and Coding Manual (ICSD-2), but there is debate about its classification.

There are a few other similaritiesamongst catathrenia sufferers that have not yet been studied properly:

- Many catathrenia sufferers mention that they also suffer from some form of stress or anxiety in their lives.

- Sufferers themselves do not feel like they are experiencing a sleep apnea; the breath-holding appears to be controlled though the unconscious. Oxygen desaturation during a catathrenia episode is usually negligible.

- Many took part in sports activities during teens and twenties some which required breath-holding which included many types of sports such as swimming and even weight lifting. They find a certain level of comfort in breath-holding, and often do it while awake.

- Observations have been made of instances of breath holding during daily activities that require concentration.

- Some sufferers recalled suffering from lucid or stress dreams during their catathrenia episodes during their sleep.

- Some sufferers complain of having a painful chest upon waking from sleep.

Because catathrenia itself is not considered life-threatening, there has been very little research done in the medical community, and many experts assume that the way to treat catathrenia is to treat the underlying sleep apnea, though there is no conclusive evidence published that catathrenia results from sleep apnea, and sleep studies show that not all sufferers of catathrenia have been diagnosed with sleep apnea.

While doctors tend to dismiss it as an inconvenience, sufferers routinely describe the condition's highly negative effects on their daily lives including tiredness, low energy, dizziness and vertigo, work problems, relationship and social issues, and other physical and mental problems that could be associated with low sleep quality.

Recurrent Isolated Sleep Paralysis is an inability to perform voluntary movements at sleep onset, or upon waking from sleep.

REM sleep behavior disorder or RBD is the most common REM sleep parasomnia in which muscle atonia is absent. This allows the individual to act out their dreams and may result in repeated injury—bruises, lacerations, and fractures—to themselves or others. Patients may take self-protection measures by tethering themselves to bed, using pillow barricades, or sleeping in an empty room on a mattress.

Demographically, 90% of RBD patients are males, and most are older than 50 years of age.

Typical clinical features of REM sleep behavior disorder are:

- Male gender predilection

- Mean age of onset 50–65 years (range 20–80 years)

- Vocalisation, screaming, swearing that may be associated with dreams

- Motor activity, simple or complex, that may result in injury to patient or bed-partner

- Occurrence usually in latter half of sleep period (REM sleep)

- May be associated with neurodegenerative disease

Acute RBD, occurs mostly as a result of a side-effect in prescribed medication—usually antidepressants. But if not then 55% of the time the cause is unknown the other 45% the cause is associated with alcohol.

Chronic RBD is idiopathic, meaning of unknown origin, or associated with neurological disorders. There is a growing association of chronic RBD with neurodegenerative disorders—Parkinson's disease, multiple system atrophy (MSA), or dementia—as an early indicator of these conditions by as much as 10 years.

Patients with narcolepsy also are more likely to develop RBD.

The most common sleep disorders include:

- Bruxism, involuntarily grinding or clenching of the teeth while sleeping.

- Catathrenia, nocturnal groaning during prolonged exhalation.

- Delayed sleep phase disorder (DSPD), inability to awaken and fall asleep at socially acceptable times but no problem with sleep maintenance, a disorder of circadian rhythms. Other such disorders are advanced sleep phase disorder (ASPD), non-24-hour sleep–wake disorder (non-24) in the sighted or in the blind, and irregular sleep wake rhythm, all much less common than DSPD, as well as the situational shift work sleep disorder.

- Hypopnea syndrome, abnormally shallow breathing or slow respiratory rate while sleeping.

- Idiopathic hypersomnia, a primary, neurologic cause of long-sleeping, sharing many similarities with narcolepsy.

- Insomnia disorder (primary insomnia), chronic difficulty in falling asleep and/or maintaining sleep when no other cause is found for these symptoms. Insomnia can also be comorbid with or secondary to other disorders.

- Kleine–Levin syndrome, a rare disorder characterized by persistent episodic hypersomnia and cognitive or mood changes.

- Narcolepsy, including excessive daytime sleepiness (EDS), often culminating in falling asleep spontaneously but unwillingly at inappropriate times. About 70% of those who have narcolepsy also have cataplexy, a sudden weakness in the motor muscles that can result in collapse to the floor while retaining full conscious awareness.

- Night terror, "Pavor nocturnus", sleep terror disorder, an abrupt awakening from sleep with behavior consistent with terror.

- Nocturia, a frequent need to get up and urinate at night. It differs from enuresis, or bed-wetting, in which the person does not arouse from sleep, but the bladder nevertheless empties.

- Parasomnias, disruptive sleep-related events involving inappropriate actions during sleep, for example sleep walking, night-terrors and catathrenia.

- Periodic limb movement disorder (PLMD), sudden involuntary movement of arms and/or legs during sleep, for example kicking the legs. Also known as nocturnal myoclonus. See also Hypnic jerk, which is not a disorder.

- Rapid eye movement sleep behavior disorder (RBD), acting out violent or dramatic dreams while in REM sleep, sometimes injuring bed partner or self (REM sleep disorder or RSD).

- Restless legs syndrome (RLS), an irresistible urge to move legs. RLS sufferers often also have PLMD.

- Shift work sleep disorder (SWSD), a situational circadian rhythm sleep disorder. (Jet lag was previously included as a situational circadian rhythm sleep disorder, but it doesn't appear in DSM-5 (see Diagnostic and Statistical Manual of Mental Disorders)).

- Sleep apnea, obstructive sleep apnea, obstruction of the airway during sleep, causing lack of sufficient deep sleep, often accompanied by snoring. Other forms of sleep apnea are less common. When air is blocked from entering into the lungs, the individual unconsciously gasps for air and sleep is disturbed. Stops of breathing of at least ten seconds, 30 times within seven hours of sleep, classifies as apnea. Other forms of sleep apnea include central sleep apnea and sleep-related hypoventilation.

- Sleep paralysis, characterized by temporary paralysis of the body shortly before or after sleep. Sleep paralysis may be accompanied by visual, auditory or tactile hallucinations. Not a disorder unless severe. Often seen as part of narcolepsy.

- Sleepwalking or "somnambulism", engaging in activities normally associated with wakefulness (such as eating or dressing), which may include walking, without the conscious knowledge of the subject.

- Somniphobia, one cause of sleep deprivation, a dread/ fear of falling asleep or going to bed. Signs of the illness include anxiety and panic attacks before and during attempts to sleep.

A systematic review found that traumatic childhood experiences (such as family conflict or sexual trauma) significantly increases the risk for a number of sleep disorders in adulthood, including sleep apnea, narcolepsy, and insomnia. It is currently unclear whether or not moderate alcohol consumption increases the risk of obstructive sleep apnea.

In addition, an evidence-based synopses suggests that the sleep disorder, idiopathic REM sleep behavior disorder (iRBD), may have a hereditary component to it. A total of 632 participants, half with iRBD and half without, completed self-report questionnaires. The results of the study suggest that people with iRBD are more likely to report having a first-degree relative with the same sleep disorder than people of the same age and sex that do not have the disorder. More research needs to be conducted to gain further information about the hereditary nature of sleep disorders.

A population susceptible to the development of sleep disorders is people who have experienced a traumatic brain injury (TBI). Because many researchers have focused on this issue, a systematic review was conducted to synthesize their findings. According to their results, TBI individuals are most disproportionately at risk for developing narcolepsy, obstructive sleep apnea, excessive daytime sleepiness, and insomnia. The study's complete findings can be found in the table below:

Sleeping in a more upright position seems to lessen catathrenia (as well as sleep apnea). Performing regular aerobic exercise, where steady breathing is necessary (running, cycling etc.) may lessen catathrenia. Strength exercise, on the other hand, may worsen catathrenia because of the tendency to hold one's breath while exercising. Yoga and/or meditation focused on steady and regular breathing may lessen catathrenia.