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Cognitive decline can continue up to 10 years after psychosis onset

Adults with schizophrenia and other psychoses continue to experience cognitive decline after illness onset; however, the nature of this decline differs across neuropsychological functions, according to data from a 10-year prospective study published in American Journal of Psychiatry.

“While it is widely believed that cognitive impairments stabilize after illness onset, at least until older adult life, few longitudinal studies have examined cognitive change from illness onset through to a decade later, and findings across studies and cognitive domains are mixed,” Jolanta Zanelli, PhD, from the department of psychosis studies, Institute of Psychiatry, Psychology and Neuroscience, King’s College London, and colleagues wrote.

To determine cognitive change over time in psychosis, researchers investigated whether patients with schizophrenia experience cognitive decline after the first episode, whether this decline occurred across multiple cognitive domains (ie, verbal knowledge, memory, language, processing speed, executive function/working memory, and visuospatial ability) and whether decline was specific to schizophrenia.

Participants from a population-based case-control study with first-episode psychosis were followed prospectively up to 10 years after first admission. The investigators conducted a neuropsychological assessment, which measured IQ and specific cognitive functions, at index presentation and at follow-up to 65 patients with schizophrenia, 41 with other psychosis and 103 healthy comparison subjects.

The results showed a greater decline in IQ among patients with schizophrenia than among comparison subjects, who showed no signs of decline (effect size = –0.28; 95% CI, –0.47 to –0.09), as well as a greater cognitive decline across tests in memory and verbal knowledge domains. However, the schizophrenia group showed no significant cognitive changes in processing speed and executive function domains compared with controls.

“While large deficits in processing speed are already apparent at the first episode, deficits in verbal knowledge and memory continue to increase,” the researchers wrote. “These findings suggest that different pathophysiological mechanisms may underlie individual neuropsychological deficits seen in adult psychosis patients.”

In addition, Zanelli and colleagues found that memory-related decline was not specific to schizophrenia and was evident in patients with other psychoses as well. The other psychoses group demonstrated greater declines than comparison subjects across tests in the memory domain, particularly in verbal learning (P = .001), similar to the schizophrenia group. Also, like patients in the schizophrenia group, those with other psychoses showed deficits in tests of processing speed, executive functions and working memory, and visuospatial ability.

“Future research should determine which of these are consequent to the illness itself, and which to the psychosocial factors patients experience,” Zanelli and colleagues wrote. “These findings highlight the importance of targeting early developmental stages in future studies of the causes of cognitive deficits associated with psychosis, as well as in cognitive remediation efforts.” – by Savannah Demko

Disclosure: Zanelli reports no relevant financial disclosures. Please see the study for all other authors’ relevant financial disclosures.