Sleepwalking sussed?

Imagine suddenly waking up in the open air and not knowing where you are: it’s a real prospect for those who suffer from sleepwalking.

Sleepwalkers can leave the house and roam, putting themselves in danger Credit Flickr/practicalowl

Sleepwalking – or somnambulism – tends to run in families, and by studying four generations of family, scientists in America think they have discovered the genetic code that causes people to suffer from the condition.

Dr Christina Gurnett and colleagues at the Washington School of Medicine took saliva samples from four generations of a family – spanning from the grandparents downward – who had been referred to them because one of the youngest members of the family, a 12-year-old girl, had troublesome sleepwalking. Nine of the 22 family members were sleepwalkers.

A genome-wide search revealed the problem stemmed from the genetic code housed on chromosome 20 which had been passed down from generation to generation. Someone with the gene has a 50% chance of passing it on to their children, and any individual inheriting a copy of the faulty DNA would be a sleepwalker.

Although the precise genes have yet to be identified, the scientists’ hunch is that it will be the adenosine deaminase gene that is the culprit. The gene is already known to be linked to the deep, dreamless “slow wave”– the non-rapid eye movement – stage of sleep.

“It’s likely that several genes will be involved. What we have found is the first genetic locus for sleepwalking,” said Gurnett. “We do not know yet which if the genes in this linkage region of chromosome 20 will be responsible. Until we find the gene we won’t know whether this accounts for several families or a large number of families who have sleepwalking.

Gurnett hopes discovering the genes could help with identifying and treating the condition – which affects up to 19% of children and 1 in 50 adults.