Researchers find that children with obsessive-compulsive disorder are more likely to have antibodies associated with streptococcal infection than those without the disorder.

The joint Institute of Psychiatry and Institute of Neurology team says that more research is needed.

The findings are reported in the British Journal of Psychiatry

About 3% of the population suffers from the anxiety disorder, which is generally treated by drugs or cognitive behavior therapy counseling.

Researchers tested the blood of 50 children with OCD for the presence of anti-basal ganglia antibodies, which are produced when antibodies raised in response to a streptococcus infection react with part of the brain.

Such an immune response is closely linked to movement disorders, such as Sydenham's chorea, which themselves are linked to OCD.

The team found that 42% of the OCD children had the antibodies, compared to just 5% of the 190-strong control group.