ASP vs Narcolepsy
Guilt by Association
ASP has been reported, under any number of names, since the days of antiquity. Unfortunately, it was first described within the current medical tradition in 1876, about 80 years before the connection between ASP and REM sleep became known. It came to be considered an abnormal condition, and, in 1928, it was first associated with narcolepsy, a serious illness requiring medical care. Eventually, it became part of the so-called narcoleptic "Tetrad" that supposedly defined the symptoms of narcolepsy, the others being:
- sleep attacks: the sudden onset of REM-state sleep
- cataplexy: the sudden loss of muscle control leading to falls
- hynagogic imagery: vivid dream-like imagery
However, once it became possible to monitor the brain wave activity of sleepers, it was discovered that sleep paralysis occurs in narcoleptics only during a Sleep Onset Rapid Eye Movement Period [SOREMP].
Usually, the body dives into deep sleep and only rises to the state of REM sleep about 90 minutes later and about every 90 minutes thereafter. However, various conditions can increase the risk/chance of having a Sleep Onset Rapid Eye Movement Period, and one could ask whether people who did not suffer from narcolepsy would experience Awareness during Sleep Paralysis events during a SOREMP if one could be induced.
In one study, a team of Japanese researchers selected 16 college students who were known to have experienced kanashibari, the Japanese folk expression for Sleep Paralysis, but who showed no signs of narcolepsy. The researchers induced sleep onset REM periods by the simple technique of interrupting the subject's sleep. SOREMPs were reported in 71.9% of these attempts and Awareness during Sleep Paralysis occurred in 9.4% of those induced REM periods.
Another team of Japanese researchers concluded that the high prevalence of kanashibari among Japanese college students indicated "that sleep paralysis is a physiological phenomenon rather than a pathological one."
This strongly suggests that ASP is a function of REM-sleep, no matter how this state is induced, and is not itself a disease.