New Scientist reveals a possible irony of microbiology. It could be that obsessive-compulsive disorder – in which the brain gets stuck in loops of repetitive, ritualistic activity, like hand-washing or counting everyday objects – is caused by Streptococcus bacteria:
The immune system eventually catches on and makes antibodies to the proteins – but these can then attack human tissue including the heart, joints and brain. This has long been known to cause heart disease and a nervous disorder called Sydenham’s chorea.
In children, it emerged several years ago that this attack on the brain can inflame brain structures called the basal ganglia, and may precipitate a syndrome whose symptoms include obsessive thoughts and compulsive rituals, identical to the psychological condition obsessive-compulsive disorder.
The NIMH has now launched a project to find such cases and improve diagnosis and treatment, including a study to see how well IVIG, a human antibody treatment used to dampen autoimmune reactions, reverses the syndrome.