Image
© RexSleepwalkers can be injured during their nighttime wandering. Scientists believe they may have discovered one genetic cause of the disorder
It's a disorder that can be embarrassing and even dangerous, but scientists now believe they have discovered one of the secrets behind sleepwalking.

Researchers studied four generations of a family where nine members out of 22 had the condition.

They found that all the sufferers had a fault on a particular chromosome and carrying just one copy of this defective DNA was enough to cause sleepwalking.

The team from Washington University, led by Dr Christina Gurnett, hope the findings will help create new treatments.

Sleepwalking affects one in 10 children and around one in 50 adults. If a person with the condition is disturbed during the night, the primitive parts of their brain can spring into life while the conscious controlling part do not.

This can cause them to sit up, walk around and complete complex tasks, all while asleep.

Those with the condition, also known as somnambulism, may perform benign activities such as pulling on a pair of socks. However, there have been cases where sleepwalkers have been killed after walking into a busy road or they have injured a family member.

Little is known about what causes sleepwalking although stress and fatigue are known triggers. Episodes usually come on early in the night and can last from seconds to hours with the sufferer unable to remember the event when they wake.

In the latest study, scientists looked at a family where half were prolific sleepwalkers. While one man put on eight pairs of socks each night his 12-year-old niece regularly roamed the streets. Many of the relatives had suffered from broken toes after stumbling in their sleep.

Analysing saliva samples, the researchers found the problem stemmed from a fault on chromosome 20, which was passed down the family. They said more work was needed to pin down the exact genes involved.

Dr Gurnett told the BBC: 'It is likely that several genes will be involved. What we have found is the first genetic locus for sleepwalking.

'We do not know yet which of 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.

'But discovering these genes could help with identifying and treating the condition.'