When people are stricken with chicken pox, poison ivy or any other maddeningly itchy condition, they might resort to scratching in their sleep. It makes sense: during rest, we lack the impulse control that prevents us from consciously clawing away at the site of the itch. But some people without any apparent skin disorder wake up to discover self-induced abrasions on their bodies. Sleep scientists want to upgrade the undiagnosable habit to a full-fledged parasomnia, among the likes of sleep-walking and sexomnia.
Definitions for parasomnias aren’t particularly precise. According to the International Classification of Sleep Disorders, parasomnias are “undesirable physical events or experiences that occur during entry into sleep, within sleep or during arousal from sleep.” At another point, the classification says parasomnias “comprise disorders that intrude into or occur during sleep and that are not primarily disorders of the states of sleep and wakefulness per se.”
Considering these general characterizations, it’s surprising that there aren’t more bids to classify nocturnal behaviors as parasomnias. But those pushing to label sleep-scratching as a diagnosable issue aren’t simply arguing that it’s a harmful mid-sleep compulsion. Researchers at the University of Michigan Sleep Disorders Laboratory state in a new paper that sleep-scratching can occur as a distinct behavior, rather than merely a symptom of a dermatological condition or another parasomnia. In other words, sleep-scratching isn’t a sign of, and isn’t used to diagnose, sleep- walking, -eating or -sexing.
The paper, published in the Journal of Clinical Sleep Medicine, presents three case studies of sleep clinic patients prospectively eligible for the not-yet-existing diagnosis: a 68-year-old man, a 68-year-old woman and a 40-year-old woman, whose sleep-scratching episodes include overlapping features. The older woman reported scratching her feet and legs but bore no visible abrasions; the other two, meanwhile, went for their faces. No one scratched during the day or had a skin condition that might explain the episodes, although the male scratcher had seen a dermatologist to no avail. Of the three, two had a history of depression and two suffered from chronic pain. During monitored sleep tests, all three exhibited disordered breathing characteristic of sleep apnea.
Treatment for sleep apnea (a CPAP mask worn overnight) didn’t do anything to end the scratching. Medication, however, had some effect. The sole male said he was cured of his itching ails after a month of taking benzodiazepine clonazepam. The older woman was prescribed gabapentin, often used to treat seizures, and reported some improvement. The third woman, however, declined treatment for scratching and stopped wearing her sleep apnea mask due to reported claustrophobia and panic attacks.
Taken together, the three cases suggested a few things to researchers. First, the underlying cause of nighttime itching could have something to do with irregular circadian rhythms in skin tissue cells. Second, they also saw chronic pain and depression as relevant and found evidence of some overlap between pain and itch receptors. (Painkillers make this connection apparent — in dulling pain, opioids like Vicodin can cause intense itching). Finally previous research has linked depressed moods with a heightened perception for itching. Additional legwork is needed to pin down the underlying cause, but study authors believe they can make sleep-related scratching its own parasomnia — and, hopefully, lessen the urge to itch.