KEY POINTS:
Sleepwalkers are rarely violent and do not seek out victims while they are in a sleep arousal state, research shows.
The review of medical and legal literature on 32 cases found that if a sleepwalker does become violent, the victim is usually someone who got in the way,
rather than the target of premeditated violence.
"Sleepwalkers are not inherently violent," said study author Mark Pressman, of Lankenau Hospital in Wynnewood, Pennsylvania. "Sleepwalking violence is quite rare."
There's sort of a cartoon-like conception in the general public that sleepwalkers get out of bed with a knife and go looking for someone they're angry with.
But he said this perception was off base. Sleepwalkers were functioning at a low level, with the parts of their brains responsible for planning and socialisation out of commission. "Legal cases in which the defendant supposedly went somewhere and sought out the victim are not likely to be true cases of sleepwalking," said Dr Pressman, who has acted as an expert witness in such cases.
He undertook his review, published in the journal Sleep, to test the hypothesis that sleepwalkers may harm people who touch them or are close by, but they don't spontaneously attack other people. For centuries, he noted, there have been reports of violent acts by sleepwalkers, and even cases of people acquitted of murder because they claimed to have been asleep when they committed the act.
He divided the cases into three categories: sleepwalking; confusional arousal, a state identical to sleepwalking but the sleeper doesn't leave the bed; and sleep terrors, or sudden partial awakening due to a frightening stimulus, followed by sleepwalking.
In all of the confusional arousal cases, the victim of violence had been close to or touching the attacker, the research found, and the same was true in 81 per cent of sleep terror cases and 40 to 90 per cent of the sleepwalking cases.
"Often the provocation was quite minor and the response greatly exaggerated," he noted.
Sleepwalking appeared to occur when something "goes bump in the night" but a person did not wake up fully in response, Dr Pressman said. Genetics appear to be involved, as sleepwalking often runs in families. Up to 15 per cent of children sleepwalk but the majority grows out of it.
Dr Pressman said the old advice that people should not wake a sleepwalker was misguided because it was actually quite difficult to do so. The best way to cope with sleepwalkers was to speak to them in a clear voice - using simple language - and try to steer them away from dangerous situations and back into bed. And touch and approach them with care. Dr Pressman said: "There certainly is a possibility if you have a sleepwalker who is big enough to inflict damage and you grab them and you block them they may not respond as you expect, probably because they don't even recognise who you are."
- Reuters