Sleepwalking might seem like an isolated phenomena that only few people suffer from, but it may be more common that previously thought — especially among those who take sleep aids.

A sleep study conducted by the Stanford University Sleep Epidemiology Research Center and published in the journal Neurology polled 16,000 adults across 15 states on their sleepwalking history. Thirty percent of the subjects reported an incident of sleepwalking in childhood or adolescence, while 3.6 percent claimed to have sleepwalked at least once the previous year. Thirty percent of children sleepwalk at some point in their lives.

It works out to about 8.5 million adults who sleepwalk. People on medicines like antidepressants are more likely to sleepwalk, too. Those on medication tend to sleepwalk twice as often as those who are not. Ironically, enough, those taking over-the-counter sleeping pills tend to sleepwalk at a rate of almost three times more.

Surprisingly, there was no discernible link between prescription sleep aids and sleepwalking in this study. Other studies have previously shown a link. The fact that fewer people take prescribed sleeping pills and more take over-the-counter could account for the difference in sleepwalking.

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