June 14, 2012 | 3 Last month, psychiatrists at Stanford
University announced that sleepwalking is on the rise. More than
8.4 million adult Americans—3.6 percent of the population over
18—are prone to sleepwalking. That’s up from a 2 percent
prevalence the same authors found a decade ago. And as the
latest issue of Scientific American Mind notes, a subset of
these nighttime wanderers may be at risk for a disturbing and
dangerous phenomenon: sleep violence. Aggressive somnambulance
in the general population hovers at or below 2 percent in
surveys conducted in North America and Europe. But not all
sleepwalkers exhibit violent behavior and what causes the
violence remains a puzzle to researchers. In fact, three
separate disorders are associated with sleep violence. In
arousal disorders—discussed in-depth in this month’s feature—an
individual operates in a mental state between wakefulness and
sleep, carrying out complex behaviors with no evident conscious
awareness. In comparison, people with nocturnal frontal lob