Is there change in intelligence quotient in chronically ill schizophrenia patients? A longitudinal study in twins discordant for schizophrenia

Hedman, Anna M.; Haren, Neeltje E.M. van; Baal, G. Caroline M. van; Brans, Rachel G.H.; Hijman, Ron; Kahn, René S.; Pol, Hilleke E. Hulshoff

doi:10.1017/s0033291712000694

Cited by 10 publications

(7 citation statements)

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“…Apart from this, deficits in global measures of cognition such as intelligence are common in SZ patients (74, 75). On the other side, it is a well-established finding that IQ levels do not change over the course of illness and that lower IQ is a stable trait in patients suffering from SZ (76–78). Furthermore, variables such as education, occupation, and age can contribute significantly to IQ values (79).…”

Section: Discussionmentioning

confidence: 99%

Neurological Abnormalities in Recent-Onset Schizophrenia and Asperger-Syndrome

et al. 2014

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Background: Neurological abnormalities including a variety of subtle deficits such as discrete impairments in sensory integration, motor coordination (MOCO), and sequencing of complex motor acts are frequently found in patients with schizophrenia (SZ) and commonly referred to as neurological soft signs (NSS). Asperger-syndrome (AS) is characterized by sensory-motor difficulties as well. However, the question whether the two disorders share a common or a disease-specific pattern of NSS remains unresolved.Method: A total of 78 age- and education-matched participants [26 patients with recent-onset SZ, 26 individuals with AS, and 26 healthy controls (HC)] were recruited for the study. Analyses of covariance (ANCOVAs), with age, years of education, and medication included as covariates, were used to examine group differences on total NSS and the five subscale scores. Discriminant analyses were employed to identify the NSS subscales that maximally discriminate between the three groups.Results: Significant differences among the three groups were found in NSS total score and on the five NSS subscales. The clinical groups differed significantly in the NSS subscale MOCO. The correct discriminant rate between patients with SZ and individuals with AS was 61.5%. The correct discriminant rate was 92.3% between individuals with AS and HC, and 80.8% between SZ patients and HC, respectively.Conclusion: Our findings provide new evidence for the presence of NSS in AS and lend further support to previously reported difficulties in movement control in this disorder. According to the present results, SZ and AS seem to be characterized by both quantitative and qualitative NSS expression.

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Section: Discussionmentioning

confidence: 99%

Neurological Abnormalities in Recent-Onset Schizophrenia and Asperger-Syndrome

et al. 2014

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“…Using a twin design, Hedman et al . (2012) reported a lack of increase in IQ in patients, not in co-twins, indicating that in chronically ill patients environmental factors implicated in the disease are associated with a lack of IQ improvement over time.…”

Section: Introductionmentioning

confidence: 99%

Change in IQ in schizophrenia patients and their siblings: a controlled longitudinal study

2019

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BackgroundLower intelligence quotient (IQ) has frequently been reported in patients with schizophrenia. However, it is unclear whether IQ declines (further) after illness onset and what the familial contribution is to this change. Therefore, we investigate IQ changes during the course of illness in patients with non-affective psychosis, their siblings and controls.MethodsData are part of the longitudinal Genetic Risk and Outcome of Psychosis (GROUP) study in the Netherlands and Belgium. Participants underwent three measurements, each approximately 3 years apart. A total of 1022 patients with non-affective psychosis [illness duration: 4.34 (s.d. = 4.50) years], 977 of their siblings, and 565 controls had at least one measure of IQ (estimated from four subtests of the WAIS-III).ResultsAt baseline, IQ was significantly lower in patients (IQ = 97.8) and siblings (IQ = 108.2; p < 0.0001) than in controls (IQ = 113.0; p < 0.0001), and in patients as compared with siblings (p < 0.0001). Over time, IQ increased in all groups. In siblings, improvement in IQ was significantly more pronounced (+0.7 points/year) than in patients (+0.5 points/year; p < 0.0001) and controls (+0.3 points/year; p < 0.0001). IQ increase was not significantly correlated with improvement in (sub)clinical outcome in any of the groups.ConclusionsDuring the first 10 years of the illness, IQ increases to a similar (and subtle) extent in a relatively high-functioning group of schizophrenia patients and controls, despite the lower IQ in patients at baseline. In addition, the siblings’ IQ was intermediate at baseline, but over time the increase in IQ was more pronounced.

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“…[9][10][11][12][13][14][15] Cognitive deficits constitute a core symptom of schizophrenia, 16 with general intelligence already affected prior to onset of psychotic symptoms, 17 declining after the first psychotic episode, 18 and lacking normal gain in global cognitive abilities over time. 19,20 The intelligence quotient (IQ) is one of the most heritable cognitive phenotypes, with ~80% of the variance explained through additive genetics. 21 Using a discordant twin design, it was shown that schizophrenia and IQ share a partially overlapping genetic background.…”

Section: Introductionmentioning

confidence: 99%

Genetic Variation in Schizophrenia Liability is Shared With Intellectual Ability and Brain Structure

Bohlken

Brouwer

Mandl

et al. 2016

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Is there change in intelligence quotient in chronically ill schizophrenia patients? A longitudinal study in twins discordant for schizophrenia

Abstract: Patients with schizophrenia in the chronic phase of the disease, but not the discordant co-twins, show a lack of increase in IQ, which is probably due to environmental (non-genetic) factors related to the disease.

Cited by 10 publications

References 42 publications

Neurological Abnormalities in Recent-Onset Schizophrenia and Asperger-Syndrome

Neurological Abnormalities in Recent-Onset Schizophrenia and Asperger-Syndrome

Change in IQ in schizophrenia patients and their siblings: a controlled longitudinal study

Genetic Variation in Schizophrenia Liability is Shared With Intellectual Ability and Brain Structure

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