Some cases of mental illness in human beings may have a viral origin, say a group of German researchers. They have found traces of genetic material of a virus -- which makes horses hyperactive -- in the blood cells of people with depression and other mental disorders.

The discovery of the Borna Disease Virus (BVS) genetic material in the blood cells of psychiatric patients suggests that some of them may have been exposed to the virus. Very recently, 2 American teams found that upto 30 per cent of people with schizophrenia carry antibodies of BDV virus.