Dec. 11 (UPI) -- People receiving treatment for schizophrenia and bipolar disorder may experience a gradual loss of cognitive function -- including declines in verbal skills -- over the course of their illness, the results of a new analysis suggest.

The findings, published Wednesday in the JAMA Psychiatry, go at least some way toward answering what has been a "contentious" question among mental health professionals for decades, according to study co-author Roman Kotov: Do psychotic disorders, particularly schizophrenia, improve cognitive function or cause it to decline?


"This is not a new question, but we finally have the data to shed much light on it," Kotov, a professor of psychiatry and behavioral health at Stony Brook University Renaissance School of Medicine, told UPI.

To do so, Kotov and his colleagues assessed the cognitive function of 705 adults, 445 of whom had been diagnosed with psychotic disorders, namely: schizophrenia-spectrum, affective psychoses -- including bipolar disorder -- or other psychoses. Those who had been diagnosed with psychotic disorders were assessed once, two years after their first hospitalization for mental health-related services, and again 20 years later.

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The 260 controls -- or those who hadn't been diagnosed with a psychotic disorder -- were assessed at similar periods to generate comparable findings.

"Cognitive functioning changes slowly -- short of extreme situations like a stroke -- so you need to follow people for years to detect it," Kotov explained.

The authors analyzed change in cognitive functioning in six "domains" -- verbal knowledge, verbal declarative memory, visual declarative memory, attention and processing speed, abstraction-executive function and verbal fluency.

Overall, they found that cognitive function declined in all but two of these areas -- verbal knowledge and abstraction-executive function -- by as much as 30 percent in those with a diagnosed psychotic disorder, with the most significant reduction generally seen among those with affective psychoses. However, most of the declines documented by the researchers were "modest," Kotov said.

"Plenty of patients did better than average and some definitely improved," he added. "Unfortunately, there is no established treatment for cognitive limitations, but healthy lifestyle -- especially, physical activity -- and active social life -- avoiding loneliness and isolation -- are the best" ways to reduce individual risk for them, both in those with and without psychotic disorders.

The National Institutes of Mental Health estimates that as many as 2.1 million Americans are schizophrenic, while more than 9 million have bipolar disorder. The agency emphasizes that exact figures on those with mental illnesses have been hard to pin down -- given the social stigma that surrounds them and the resulting reluctance of some to pursue treatment.

Although the findings published Wednesday may be troubling for many of those with these and other similar conditions, Kotov noted that additional research is needed to better understand the cause of any cognitive decline related to these disorders.

For now, "I can speculate that activity -- going new places, interacting with new people, and getting a workout -- are far better for brain health than staying home day after day," he said. "This is easier said than done, and help of family members often is crucial. Management of one's health is complicated and requires a lot of effort; people with psychotic disorders often need a hand in this."