London, Nov 27 (UNI) Scientists have discovered new evidence on why obsessive compulsive disorder (OCD) runs in families.
In the latest study, researchers tried to determine whether there were biological markers of genetic risk for developing OCD.
They studied people with OCD and their close family members and found they shared distinctive patterns in their brain structure.
OCD is known to run in families but little is known about how genes contribute to the disorder, although one theory is they may influence brain structure.
The experts, from the University of Cambridge, said it was the first time an anatomical trait had been linked with familial risk for the disorder.
Their findings, published in the journal Brain, could help predict risk and lead to more accurate diagnosis of OCD.
Using magnetic resonance imaging (MRI), they took pictures of the brains of 31 people with OCD as well as scans of 31 healthy close relatives (such as a brother, sister or parent). A second group of 31 healthy people acted as controls.
Those involved also took a computerised test which meant pressing a left or right button as quickly as possible when arrows appeared.
When a beep noise sounded, they had to try and stop their responses, with the aim of measuring their ability to halt repetitive behaviours.
The results showed that OCD sufferers and their families performed the computer task less well and also had less grey matter in the areas of their brain associated with suppressing responses.
The researchers concluded they had found ''substantial evidence that variation in motor inhibitory control''was correlated with grey matter density changes in parts of the brain.
Lara Menzies from the Brain Mapping Unit at the University of Cambridge said: ''Impaired brain function in the areas of the brain associated with stopping motor responses may contribute to the compulsive and repetitive behaviours that are characteristic of OCD.
''These brain changes appear to run in families and may represent a genetic risk factor for developing the condition,'' Ms Menzies said.
''The current diagnosis of OCD available to psychiatrists is subjective and therefore knowledge of the underlying causes may lead to better diagnosis and ultimately improved clinical treatments.'' she adeded.
People suffering from OCD experience recurrent thoughts about subjects such as contamination and germs.
They may also take part in rituals, such as repeated hand-washing, checking windows are locked or lining items up in a specific order.