Parasomnia refers to a diverse group of sleep disorders characterized by undesirable physical events or experiences that occur during sleep, as a person is falling asleep, or while they are waking up. These phenomena can include abnormal movements, behaviors, perceptions, emotions, and dreams that disrupt the continuity of rest. This article explores the nature of parasomnias and their classification within modern medical frameworks.
Defining Parasomnia and Its Classification
Parasomnia is definitively classified as a Sleep-Wake Disorder, not a primary mental illness. Major diagnostic manuals, such as the DSM-5 and the ICD-11, place them in the category of sleep disorders. This classification emphasizes that the root cause is a physiological dysfunction in the brain’s sleep-wake cycle regulation.
The core mechanism involves a state of “dissociated sleep,” where parts of the brain exhibit characteristics of wakefulness, while other parts remain in a sleep state. This partial arousal leads to the complex, often bizarre, behaviors associated with parasomnias. Although these disorders can cause significant psychological distress or co-occur with mental health conditions, the primary pathology is neurological, not psychiatric. The DSM-5 lists Non-Rapid Eye Movement (NREM) Sleep Arousal Disorders and Rapid Eye Movement (REM) Sleep Behavior Disorder as distinct entities under the Sleep-Wake Disorders section.
Categories of Parasomnia
Parasomnias are primarily grouped based on the stage of the sleep cycle during which the abnormal event occurs. The two main categories are NREM-related and REM-related parasomnias.
NREM-related parasomnias, often termed disorders of arousal, occur during the deeper stages of sleep, typically in the first half of the night. These include sleepwalking (somnambulism) and sleep terrors (night terrors), where the person is only partially awake and exhibits complex motor activity. Individuals experiencing these episodes are generally unresponsive to external efforts to communicate and usually have no memory of the event upon fully waking.
REM-related parasomnias occur during this stage, which is associated with vivid dreaming and muscle paralysis (atonia). The most recognized type is REM Sleep Behavior Disorder (RBD), where the normal muscle paralysis is absent or incomplete, causing the person to physically act out their dreams. These episodes tend to occur later in the night when REM periods are longer, and the individual can often recall the dream in detail when awakened. Sleep paralysis, where consciousness returns while the body remains temporarily immobilized, is also classified as a REM-related phenomenon.
Underlying Triggers and Risk Factors
The manifestation of parasomnia episodes is often influenced by a combination of predisposing factors and acute triggers. A strong genetic predisposition exists for NREM-related disorders, with a family history significantly increasing an individual’s risk for conditions like sleepwalking. Age is another factor, as NREM disorders are more common in children due to the immaturity of their central nervous system.
Several environmental and physiological factors can act as acute triggers for an episode in susceptible individuals. Sleep deprivation and an irregular sleep-wake schedule, such as those caused by shift work or jet lag, fragment the sleep architecture. The use of certain medications, including specific antidepressants and sedative-hypnotics, can interfere with normal sleep stage transitions. High levels of psychological stress, anxiety, or a concurrent fever can also destabilize the sleep state, leading to a partial arousal and an episode of parasomnia.
Managing and Treating Parasomnia
The management of parasomnia focuses on two main strategies: ensuring safety and modifying underlying causes. For complex motor behaviors like sleepwalking or REM Sleep Behavior Disorder, creating a safe sleep environment is essential to prevent injury to the individual or their bed partner. This involves measures such as securing windows and doors, removing sharp objects from the bedroom, and sleeping on a ground-floor level if possible.
Behavioral and Environmental Management
Behavioral interventions, particularly optimizing sleep hygiene, are the initial and most effective treatment for many parasomnias. Maintaining a consistent sleep schedule, avoiding alcohol and caffeine close to bedtime, and managing stress through relaxation techniques can help stabilize the sleep-wake cycle. Cognitive Behavioral Therapy for Insomnia (CBT-I) or targeted relaxation therapies may be used to address anxiety or stress that contributes to sleep fragmentation.
Medical Treatment
When episodes are frequent, dangerous, or severely disruptive to daily functioning, medical treatment may be necessary. Medications, such as benzodiazepines, are sometimes used to suppress the deep NREM or REM sleep stages where the events originate, but this is typically reserved for refractory or high-risk cases.