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25-07-2013 | Mental health | Article

IQ may forewarn of psychosis vulnerability


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medwireNews: Men with psychosis tend to have lower than average IQ, along with evidence of learning difficulties in childhood, study findings show.

“Our findings suggest that cognitive impairments, assessed in first psychotic episode, may in many cases have their origins in early life,” the researchers write in Psychiatry Research. “It supports the view of cognitive impairment as an early developmental process, which may increase the vulnerability for psychosis.”

In their study of nearly 50,000 Swiss military conscripts, aged 18 to 22 years, they found that the 61 men who had psychotic disorders diagnosed, based on their responses to a psychiatric screening questionnaire, had a significantly lower average IQ than those without mental disorders (controls), at 95.27 versus 100.64.

The reduced IQ among men with psychotic disorders was specific to performance IQ, with scores of 94.12 compared with 100.67 among controls. The corresponding scores for verbal IQ were 98.00 and 100.38.

This finding “is consistent with earlier research showing that primarily fluid functions are negatively affected in psychotic individuals,” say lead study author Mario Müller (Psychiatric University Hospital Zurich, Switzerland) and team.

Further analysis suggested that cognitive problems likely preceded the development of psychosis. For example, 12.50% of men with psychotic disorders did not complete compulsory schooling, compared with less than 1.43% of controls, 55.17% versus 22.03% had to repeat a class, and 29.82% versus 7.79% underwent psychologic review due to learning difficulties.

However, the team stresses that not all men with psychosis had a low IQ, implying that a high IQ could be protective in people with risk factors for psychosis.

Further support for the developmental model of psychosis came from the high rate of family psychiatric disorders, particularly schizophrenia, reported by men with psychotic disorders relative to controls. Low IQ, schooling problems, and family history of psychiatric disorders all remained associated with psychotic disorders after accounting for confounders.

Müller et al say their findings “may have important implications for the early detection of psychoses as well as for therapeutic approaches.” They say the results highlight “the importance of cognitive assessments in addition to simply assessing clinical symptoms of psychotic experiences,” as well as “the need for a broader therapeutic focus.”

They conclude: “Cognitive deficits may be a starting point for a personalized medicine in terms of placement, rehabilitation, medications and cognitive training.”

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

By Eleanor McDermid, Senior medwireNews Reporter

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