January 05, 2016
2 min read

Cognitive impairment differs between subclinical, clinical psychosis

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Cognitive impairment differed between adults who experienced psychosis and those with psychotic disorders, suggesting differences between subclinical and clinical psychosis, according to recent findings.

“Evidence suggests that subclinical psychotic experiences may lie on a continuum with clinically significant psychotic symptoms and therefore be informative for research into the cause of psychotic illness,” Josephine Mollon, MSc, of Institute of Psychiatry, Psychology, and Neuroscience, King’s College London, and colleagues wrote. “Lending support to this hypothesized psychosis continuum are the small neuropsychological impairments seen in people with psychotic experiences.”

To characterize neuropsychological functioning in psychotic experiences among adults, researchers evaluated 1,698 participants from the South East London Community Health study, a population-based household survey of physical and mental health in individuals aged 16 years and older. Verbal knowledge, working memory, memory and processing speed were assessed.

Overall, 171 participants experienced psychosis. They did not exhibit statistically significant impairment on mean measures of IQ or processing speed, but did on measures of verbal knowledge (P = .003), working memory (P = .005) and memory (P = .01), compared with those who did not experience psychosis.

Only participants aged 50 years and older with psychotic experiences exhibited medium-to-large impairments in neuropsychological functioning, after adjusting for socioeconomic status, cannabis use and common mental disorders.

Participants aged 35 to 49 years who experienced psychosis showed medium impairment in measures of working memory and memory, while those aged 16 to 24 years had medium impairments in verbal knowledge.

First-degree relatives of participants with psychotic experiences exhibited small impairment in verbal knowledge.

“The implications of this work could be controversial,” Ruben C. Gur, PhD, of University of Pennsylvania Perelman School of Medicine, Philadelphia, wrote in an accompanying editorial. “We uncover continuous measures that show adverse effects that do not reach the level of severity required for a symptom-based diagnosis. In community studies we document such effects in people who do not seek help. We should evaluate ways to prevent or treat these symptoms and deficits, but at what point on the continuum do we intervene and at which developmental stage? What if the treatment has adverse effects? What is the potential for abuse by applying the treatment to people who do not have a disorder but have the necessary false positive findings?” – by Amanda Oldt

Disclosure: Mollon and colleagues report no relevant financial disclosures. Gur reports receiving royalties from the Brain Resource Centre; serving without compensation on an advisory board for Lumosity; and receiving support from grants MH096891, MH105248, and R01MH107235 from the National Institute of Mental Health and grants NNX14AH27G and NNX14AH98G from the NASA.