Is Cognitive Impairment a Feature of Schizophrenia?

The majority of clients diagnosed with schizophrenia have an IQ that resides below the normal range, or declines below the normal range as the disorder progresses. “In apparent contradiction to this view, some patients with schizophrenia have been documented to have an overall IQ in the normal range, and a few have above-average performance, at least in some neuropsychological domains,” said James. H. MacCabe of the Department of Psychosis Studies at the Institute of Psychiatry at King’s College in London. “If it were truly possible to have schizophrenia with no cognitive impairment, then this would have important implications for current etiological and neuropsychological models of schizophrenia, since cognitive deficits could not be regarded as a necessary condition for the illness.”

In an effort to determine if cognitive functioning is truly a feature of schizophrenia, MacCabe evaluated 34 clients with schizophrenia and an average IQ of 120. The participants were separated into two groups, one of which had realized a decline in IQ after diagnosis, the other of which had maintained their premorbid IQ. The participants completed a series of neuropsychological tests and their results were compared to those of healthy controls and schizophrenic clients with premorbid IQ’s below the normal range. The results revealed significant differences in performance. “Schizophrenia patients whose estimated premorbid and current IQ both lay in the superior range were statistically indistinguishable from IQ-matched healthy controls on all neurocognitive tests,” said MacCabe. “However, their profile of relative performance in subtests was similar to that of typical schizophrenia patients. Patients with superior premorbid IQ and evidence of intellectual deterioration had intermediate scores.” MacCabe noted that his findings reflect those of previous studies, confirming that some individuals with superior intelligence still meet the criteria for a diagnosis of schizophrenia. He added, “Our data indicate that within these patients, some undergo a decline in cognitive functioning and develop cognitive deficits that are similar to those of typical schizophrenia patients, but of a lesser degree.”

MacCabe, J. H., Brébion, G., Reichenberg, A., Ganguly, T., McKenna, P. J., Murray, R. M., & David, A. S. (2011, December 26). Superior Intellectual Ability in Schizophrenia: Neuropsychological Characteristics. Neuropsychology. Advance online publication. doi: 10.1037/a0026376

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  • wally

    January 7th, 2012 at 7:35 AM

    Kind of surprised here- I always thought that those with schizophrenia were actually more intelligent that the average guy- wonder when the tests are given- could you possibly lose IQ points with the onset of the disease?

  • runninfast

    January 8th, 2012 at 10:23 AM

    The saddest thing about this disease is that for many they have no idea that it is going to hit and then they are slapped in the face with the symptoms almost overnight! And it always takes the ebst young people and turns them into someone that you cannot hardly even recognize anymore. But I never hear about there being a big push to find a cure for schizophrenia like you do with other diseases. It is like it is there and we all know that affects these lives but no one is talking about it like they do other things. This needs a voice that will be heard- sometimes all it takes is that one big name to get behind the cause publicly and people will start pitching in to help come up with a cure, or at least start trying out some treatments that will help make life a little more meaningful.

  • BP

    January 9th, 2012 at 1:12 PM

    A new problem in identifying schizophrenia in people would pop up because of this, although it is a good news that not everybody with schizophrenia has deterioration in their IQ.

  • Claire

    January 9th, 2012 at 4:43 PM

    IQ tests on patients in this kind of shape mean nothing.

    When there are so many other underlying problems that the patient is facing, who really cares what their intelligence level may or may not be?

    Unfortunately even if they test to be Einstein with the way that schizophrenia deteriorates the brain they are n ot going to be able to express that for very long :(

  • Rene

    January 10th, 2012 at 8:27 AM

    Wow,this does change things doesnt it?schizophrenia patients with no decline in cognitive ability!seems like it is somehow controlled by the patient s may show decline and another may not..diagnosis will only become tougher if i am not wrong..what do the experts say?

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