"When you have one episode of sleepwalking per month at minimum, you are disturbed by the disorder, no doubt," Ohayon said. "More than once a month is a lot of episodes in a year. It could be harmful for them ... because they don't have the normal reactions. So it could be a big accident coming, but happily that's very rare."
Participants who had experienced depression or obsessive-compulsive disorder were 3.5 times and 3.9 times more likely to sleepwalk, respectively, than people without the conditions, the study found. Those who took antidepressants known as SSRIs, or selective serotonin reuptake inhibitors, were three times more likely to sleepwalk twice a month or more.
Ohayon cautioned that it's not clear whether the psychiatric conditions themselves or drugs used to treat them were responsible for the heightened sleepwalking incidence.
"An association doesn't mean you have a causality link," he said. "It means at maximum, the SSRIs are triggering sleepwalking, but are not the cause. That is clear."
Participants using over-the-counter sleeping pills had a higher chance of reporting sleepwalking at least twice a month, while gender and race weren't associated with the disorder and it seemed to lessen with age.
Ohayon and Woodson agreed that longitudinal research needs to be done that can examine the long-term factors contributing to sleepwalking, which wasn't possible in this cross-sectional study.
"Sleepwalking is a really interesting phenomenon in that it represents the brain in different states -- part of the brain, in a sense, is awake, and part is asleep," Woodson said. "We're learning that other disorders may have similar brain activity . . . with mixed states of wake and sleep. I don't think we understand them all that well. Most are not associated with serious medical consequences, but obviously sometimes they can be."
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