Cause of obsessive-compulsive disorder discovered

Absence of a protein may trigger the obsessive-compulsive disorder that can lead to repetitive ritualised behaviour such as washing hands or body time and again, a new study has found.
An overactive molecular signal pathway in the brain region of the amygdala can lead to obsessive-compulsive disorder (OCD), researchers from University of Wurzburg in Germany said.
Some people have an extreme fear of dirt or bacteria. As a result, they may develop a habit of compulsive washing and repeatedly cleaning their hands or body.
They are trapped in a vicious circle, as the fear of new contamination returns quickly after washing.

Around two per cent of the general population suffer from some kind of OCD at least once in their life.
The disorder is characterised by persistent intrusive thoughts which the sufferers try to compensate for by repetitive ritualised behaviour.

Like depression, eating disorders and other mental diseases, OCD is treated with antidepressants.
However, the drugs are non-specific, that is they are not tailored to the respective disease. Therefore, scientists have been looking for new and better targeted therapies that have fewer side effects.
Professor Kai Schuh from the Institute of Physiology at Wurzburg and his team explored the underlying causes of OCD.

"We were able to show in mouse models that the absence of the protein SPRED2 alone can trigger an excessive grooming behaviour," Schuh said.
He believes that this finding is crucial as no clear trigger for this type of disorder has been identified until now.
Occurring in all cells of the body, the protein SPRED2 is found in particularly high concentrations in regions of the brain, namely in the basal ganglia and the amygdala.
Normally, the protein inhibits an important signal pathway of the cell, the so-called Ras/ERK-MAP kinase cascade. When it is missing, this signal pathway is more active than usual.

"It is primarily the brain-specific initiator of the signal pathway, the receptor tyrosine kinase TrkB, that is excessively active and causes the overshooting reaction of the downstream components," said biologist Melanie Ullrich.
Administering an inhibitor to attenuate the overactive signal cascade in the animal model improves the obsessive-compulsive symptoms.
The research was published in the journal Molecular Psychiatry.