Link found between TBE and schizophrenia

Tick-borne encephalitis (TBE), a virus spread by ticks which causes brain inflammation, can cause symptoms of schizophrenia, according to Swedish scientists.

Link found between TBE and schizophrenia
Photo: Scott Bauer

A research group at Stockholm’s Karolinska Institute has found a link between the psychiatric symptoms of TBE and those of schizophrenia.

“The link is kynurenic acid, a substance not previously believed to have any significance in the brain, but which we now suspect cause cause symptoms in people with schizophrenia,” said Lilly Schwieler, researcher at the Institute of Physiology and Pharmacology at the Karolinska Institute.

TBE is relatively common in parts of Sweden, due to the country’s large tick population.

Kynurenic acid is usually present in low concentrations in the brain, but levels of the substance rise dramatically in the central nervous systems of people with TBE. The same phenomenon is seen in people with schizophrenia.

“Kynurenic acid is a substance in the brain which, put simply, can produce confusion,” said Schwieler.

The discovery supports previous research which shows that viruses that affect the brain can cause symptoms similar to those of schizophrenia.

“We know that raised levels of kynurenic acid drastically increases levels of the signal substance dopamine, which causes symptoms of psychosis,” she said.

The research group, led by Professor Göran Engberg and Dr. Sophie Erhardt, will soon test new substances which could inhibit the production of kynurenic acid.

“If we can get such substances to work, we have a potential new drug against schizophrenia,” Schwieler said.

The research is in line with a another new study from the same lab which showed raised levels of kynurenic acid in patients with HIV-related illnesses. In this patient group, an early chronic inflammation of the brain was noticed, which in some was followed by confusion, emotional problems and psychosis.

“There is data to show a link between an activation of the immune defence system and schizophrenia,” said Schwieler.

The new research is to be presented at the Neuroscience 2007 conference in San Diego on November 6th.