Study Challenges Assumption that Schizophrenia Impairs Cognitive Ability

Secondary factors may impair performance on cognitive tasks, making it difficult for individuals diagnosed with schizophrenia to perform to the best of their ability

Shannon Peters
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A new study, led by Steffen Moritz, questions the predominant assumption that ‘schizophrenia’ causes neurocognitive impairment. Moritz is a professor and Head of the Clinical Neuropsychology Working Group in the Department of Psychiatry and Psychotherapy at the University Medical Center Hamburg-Eppendorf in Germany.

The article, recently published in Psychological Medicine, highlights secondary factors that could influence poor performance during cognitive testing, such as concerns about the assessment, fears about performing poorly, and low motivation. Moritz and colleagues challenge the stereotype that individuals diagnosed with schizophrenia are cognitively less capable than the general population.

“We must be careful not to insult patients when confronting them with test results or to induce further fears that may propagate self-stigma (e.g. giving a comorbid diagnosis of mild cognitive impairment), particularly when transient secondary influences, like medication and poor motivation cannot be ruled out,” write the researchers.

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Schizophrenia has long been associated with deficits in neurocognitive function, such as impaired memory and attention. However, cognitive impairment is not a core criterion for receiving a diagnosis of ‘schizophrenia.’ Many large studies comparing participants with schizophrenia to control subjects have confirmed significant neurocognitive deficits, with individuals diagnosed with schizophrenia performing about one standard deviation below the norm.

For example, the average IQ is 100, which means a person with an IQ of 100 performs better than 50% of the population on an IQ test. A person with schizophrenia would therefore be expected to have an IQ of 90, scoring better than 25% of the population.

Deficits in cognition have primarily been attributed to the disorder of ‘schizophrenia.’ Therefore, there is an increased focus on creating skills trainings and medications to boost cognitive functioning in this population. However, many other factors could be contributing to poor cognitive functioning, including side effects of antipsychotics and tranquilizers often prescribed for schizophrenia, or environmental factors.

In addition, many factors could reduce performance during formal cognitive testing, making the assessment an invalid measure of individuals’ abilities. For example, low motivation, test anxiety, and fear of performing poorly could all negatively impact performance. Individuals may also be distracted if they are hearing voices or having other perceptual experiences during testing.

“The literature has neglected important influences that may contribute to neurocognitive test deficits, and thus, prohibit a fair comparison between patients and controls,” write the authors.

The authors have previously conducted research investigating factors that could contribute to poor performance on cognitive tasks for patients with obsessive-compulsive disorder. Building off this research, the authors tested cognitive function in individuals with schizophrenia compared to controls using a variety of neurocognitive tasks.

Both before and after testing, participants completed the Momentary Influences, Attitudes and Motivation Impact (MIAMI) on Cognitive Performance Scale, which measures participants’ subjective experiences that could impact testing: poor motivation, concerns about the assessment, fear about having a poor outcome, and momentary influences that could impact performance (e.g., tiredness). Participants included 50 individuals diagnosed with schizophrenia currently in an inpatient psychiatric unit and 60 nonclinical controls.

All participants with schizophrenia were currently prescribed psychiatric medication, primarily second generation antipsychotics. Diagnosed participants also differed from controls on all self-report categories (e.g., concerns about assessment, fear of poor outcome, momentary influences) except they had similar motivation before the testing began.

As expected, participants diagnosed with schizophrenia performed worse on most of the cognitive tests (16 out of 18). Consistent with previous research, 2/3 diagnosed participants (compared to 1/3 of controls) performed at least one standard deviation below average on at least two tests. Only 14% of participants with schizophrenia performed two standard deviations below average.

Results show that cognitive performance was significantly correlated to scores on the MIAMI. The only exceptions were motivation before testing began and concerns about assessment after testing was completed. The researchers find, “the significant total relationship between group and neurocognition was largely mediated by MIAMI total scores.”

“If taken into account statistically, group differences in neurocognitive functioning were still detectable (= molehill) but not as huge (= mountain) as before – after correcting for subjective influences on cognitive performance, differences declined from large effects to medium,” summarize the authors.

The researchers highlight that reporting a population performs at a certain level “on average” does not negate variability in performance. Many in the population will perform above that average. They note when reporting on standard deviation, “when such findings are communicated to peers and the public, researchers often fail to highlight that results cannot be generalized to every single individual, thereby possibly increasing stigma and fears (e.g. about dementia).”

Ultimately, the authors urge researchers and clinicians conducting cognitive assessments to remember the context within which testing is done and consider the multitude of factors that impact test performance. They suggest that researchers adjust their language to highlight findings are from “a subgroup of patients” rather than generalizing to an entire population.

The researchers conclude, “due to internal (e.g. poor motivation due to a self-fulfilling prophecy), external (e.g. medication) or symptom-related (e.g. rumination, voice-hearing that distracts the individual) factors, many patients do not achieve their best performance. We need to pay closer attention to these factors before making serious recommendations.”

 

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Moritz, S., Klein, J. P., Desler, T., Lill, H., Gallinat, J., & Schneider, B. C. (2017). Neurocognitive deficits in schizophrenia. Are we making mountains out of molehills? Psychological Medicine, 47, 2602-2612. doi:10.1017/S0033291717000939 (Link)

7 COMMENTS

  1. “All participants with schizophrenia were currently prescribed psychiatric medication”, no schizophrenic patients undrugged?

    Those in authority call the drugs medicine, then the patients can not be deprived of a medicine. My third reference at the bottom of this comment “Ho acknowledges that his study is marred by the lack of a placebo control group — for ethical reasons, patients cannot be deprived of the medications they need”
    +
    “Many large studies comparing participants with schizophrenia to control subjects have confirmed significant neurocognitive deficits, with individuals diagnosed with schizophrenia performing about one standard deviation below the norm.”

    All the schizophrenics must be geniuses because of only a one point drop in IQ from the psychiatric drugs.

    1) Using Imaging to Look at Changes in the Brain. The big finding is that people with schizophrenia are losing brain tissue at a more rapid rate than healthy people of comparable age. http://www.nytimes.com/2008/09/16/health/research/16conv.html

    2) “”I looked at this test and I couldn’t have filled it in to save my life. It would have been easier to climb Mt Everest.” http://www.nzherald.co.nz/nz/news/article.cfm?c_id=1&objectid=10565099

    3) Antipsychotic drugs could shrink patients’ brains. the(brain) reduction is greatest in patients who stay on the drugs the longest . http://www.nature.com/news/2011/110207/full/news.2011.75.html

  2. “The researchers conclude, ‘due to internal (e.g. poor motivation due to a self-fulfilling prophecy), external (e.g. medication) or symptom-related (e.g. rumination, voice-hearing that distracts the individual) factors, many patients do not achieve their best performance. We need to pay closer attention to these factors before making serious recommendations.’”

    The neuroleptics create “poor motivation” via neuroleptic induced deficit syndrome, as opposed to being “due to a self-fulfilling prophecy.”

    https://en.wikipedia.org/wiki/Neuroleptic-Induced_Deficit_Syndrome

    And antipsychotics cause “voice-hearing that distracts the individual,” via anticholinergic toxidrome.

    https://en.wikipedia.org/wiki/Toxidrome

    Prior to being coerced and forced to take this neurotoxic class of drugs, I had an IQ of 136. While on this class of drugs I could not even remember my daily activities without keeping copious notes, and if I recall correctly I was tested and got a “borderline clinical” diagnosis, whatever that means. After I was taken off this neurotoxic class of drugs a potential boss (a lawyer) gave me an IQ test, I missed one on that IQ test, my lawyer boss missed 5 on the IQ test, which he also took.

    The neuroleptic drugs impair cognitive ability, and create both the negative and positive symptoms of “schizophrenia.” How long will it take for the “mental health professionals” to garner insight into this reality?

  3. “However, many other factors could be contributing to poor cognitive functioning, including side effects of antipsychotics and tranquilizers often prescribed for schizophrenia, or environmental factors.”

    It’s the effects, not any supposed “side” effects, of so-called “antipsychotics” (a marketing term) that impair performance in many domains. The drugs are technically tranquilizers and major ones at that, but their effects range from movement disorders to death, so the only descriptive name for them that is accurate is neurotoxins.

    “Twenty-eight studies reporting the various destructive effects of older antipsychotics (especially haloperidol) on brain tissue have been published in prominent neuroscience journals, based on work in animal models, cell culture, and post-mortem human tissue. Multiple molecular mechanisms, pathways, and cascades are involved, eventuating in neuronal death.”
    -Henry A. Nasrallah, MD, then editor in chief, Current Psychiatry
    http://www.mdedge.com/currentpsychiatry/article/76040/schizophrenia-other-psychotic-disorders/haloperidol-clearly

  4. So when the study compared to undiagnosed people, had these undiagnosed folks been locked up for long periods, secluded from society, deprived of intellectual stimulation, unable to pursue academic study, and regularly insulted by low intellectual expectations?

    I aced calculus when I was a kid. I can’t do math now beyond simple arithmetic simply because I haven’t used it in decades.

    Patients are not encouraged to use their intellectual abilities. Those deemed psychotic are taken out of intellectually-stimulating “groups” and put into Bingo instead. Computer use is limited on wards if allowed at all. Units ban books. (I am told my memoir is among the banned books!) Rehabs encourage low-level jobs and discourage advanced college study.

    Reading this makes me realize that taking up the intellectual exercise of writing, which I did simply to record events post-ECT, was likely the main factor that led me out of System.

    Ironically, years later I was threatened by authorities who demanded that I stop writing, the very same thing that not only liberated me, but exposed the harms that marginalized me to begin with.

    When I was midway through graduate school a doctor and social worker took me aside and said, “We know you better than you know yourself. If you go back to graduate school you will only end up back in the hospital. You must go to a day program.”

    I told them to go to hell. I went back to graduate school and did fine.