Similar memory disorders in TBE and schizophrenia

Patients with COVID-19 and tick-borne TBE are at risk of the same type of cognitive disorders with memory problems as people with schizophrenia or bipolar disorder.
The cause appears to be high levels of kynurenic acid in the brain.
Intensive Swedish research is now underway to solve the riddle that can alleviate the symptoms of these patient groups. “We have been researching for a long time to find a strategy to lower kynurenic acid in the brain,” says Lilly Schwieler, a researcher at KI.

Last year, 476 laboratory-confirmed cases of TBE in Sweden were reported to the Public Health Agency of Sweden. About 30% of those affected suffer cognitive disorders and long-term memory problems. 

According to researchers, the cause may be elevated levels of kynurenic acid in the brain after infection – something that blocks various receptors and causes memory problems. High levels of kynurenic acid are also found in patients with various psychiatric disorders – including schizophrenia and bipolar disorder. 

The higher the levels, the more confusion

Kynurenic acid is a naturally occurring substance in the brain. When produced in excess, it causes cognitive problems – such as memory problems.

Professor Sophie Erhardt and Lilly Schwieler, Senior Research Specialist at Karolinska Institutet’s Department of Physiology and Pharmacology, are leading research on kynurenic acid and cognitive disorders.

– “We have been researching for a long time to find a strategy to lower kynurenic acid in the brain. We have come a long way, but we can’t say that we are quite there yet. We are working on different mechanisms, and it may be different how to treat a person with schizophrenia with high levels of kynurenic acid in the brain and a patient with TBE or long-term COVID who has it. We may need to use different principles on how to lower the production of kynurenic acid,” says Lilly Schwieler.

“If we can achieve this, we will be very happy”

The long-term goal of the research is to find a treatment, ideally a drug, that can lower kynurenic acid levels in the brains of affected patients and mitigate the negative health aspects of TBE . 

– That’s the idea, that’s where we want to go. If we can achieve that, we will be very happy. But we don’t know if there is one drug that could be suitable for all patient groups, even if the common denominator is lowering kynurenic acid levels.

Researchers have also found that kynurenic acid levels increase in people with COVID-19, at least in the acute phase of the disease. However, how the value changes over time is less clear. 

Memory disorders second most common symptom

– We are now awaiting data to see what happens in the case of long-term COVID-19 infection, where cognitive symptoms in the form of memory disorders are the second most common symptom after breathing problems. Even in post-covid patients, fatigue combined with memory disorders is also very common. So, of course, we are also interested in studying this group more in our research,” says Lilly Schwieler.