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A MOUSE that grooms itself till its fur comes out may give us clues to what causes (OCD) in humans.

Around 2 per cent of people have OCD, but while there is thought to be a familial link, so far no genes have been found.

Now Guoping Feng at Duke University Medical Center in Durham, North Carolina, and his colleagues have created a mouse that lacks a gene called Sapap3. This is expressed in the striatum – an area of the brain that controls cognitive processes such as planning and initiating appropriate actions, and has been linked to human OCD.

While the animals looked normal, they were extremely anxious and spent up to 30 per cent of their day grooming – 10 per cent would be the norm. When the mice were given extra sapap3 protein, their abnormal behaviour disappeared (Nature, ).