A research team in the United States says that the inability to solve problems among patients with schizophrenia may be due to elevated levels of a specific compound, called kynurenic acid, in their brains.

Professor John P. Bruno, who led the study at Ohio State University, says that drugs used to suppress this compound may be an important supplement to anti-psychotic medicines, as these adjuncts could be used to treat the disorder's most resistant symptoms - cognitive impairments.

Apart from hallucinations and delusions, schizophrenia patients also have problems with what is known as cognitive flexibility or executive decision-making.

While some of them set their goals and plan ways to achieve them, they cannot adjust their thinking if circumstances force them to consider alternative strategies.

"We've got this core cluster of symptoms that is the Achilles heel for these individuals, and we're not really doing a good job of treating them," said Bruno, who teaches Psychology, Psychiatry, and Neuroscience at the university.

Bruno said that kynurenic acid is present in all human brains and has some useful functions, but excessive amounts of this compound may interfere with other chemical processes that govern the ability to pay attention and think strategically under changing conditions.

"If we try to make predictions about how disabled patients with schizophrenia will be and how likely are they to be integrated into the social fabric, it's the severity of the cognitive deficits that are most predictive. Anti-psychotics are particularly good at what we call positive symptoms, but these same drugs are very poor at treating the cognitive deficits," he said.