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28-11-2013 | Mental health | Article

Intraindividual variability may be early marker of schizophrenia


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medwireNews: Intraindividual variation (IIV) in cognitive processing is heightened in people in an at-risk mental state (ARMS) and those with schizophrenia compared with mentally healthy controls, research shows.

The study suggests that IIV offers insight into the cognitive and clinical features of ARMS that are not detectable using conventional performance measures.

“[T]he sensitive changes in response inhibition IIV observed in ARMS subjects should aid the identification of behavioral markers that can be used for detecting earlier phases of the prodromal state,” write Sung Nyun Kim (Seoul National University, Republic of Korea) and co-authors in PLoS One.

Kim’s team studied 27 people with an ARMS for psychosis, 37 patients with schizophrenia, and 38 mentally healthy controls. All participants were evaluated using the stop-signal task, which gives a measure of an individual’s ability to inhibit an ongoing motor response.

IIV in both “stop” and “go” processes was increased in ARMS subjects and schizophrenia patients relative to healthy controls. Intriguingly, however, mean performance of ARMS subjects was similar to that of healthy controls, whereas performance of schizophrenia patients was significantly impaired.

Further analysis showed that performance on the stop-signal task correlated with the severity of negative symptoms in schizophrenia patients.

The researchers say their findings “highlight the importance of considering increased IIV as a behavioral manifestation of ARMS because the IIV of cognitive processing may serve as a more sensitive index for detecting intrinsic impairment than mean-level performance.”

They add: “Understanding the early behavioral signs of ARMS subjects who have not been explicitly identified may contribute to our knowledge of the underlying pathophysiological mechanisms of schizophrenia.”

medwireNews ( is an independent clinical news service provided by Springer Healthcare Limited. © Springer Healthcare Ltd; 2013

By Joanna Lyford, senior medwireNews reporter

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