Intellectual functioning and the long-term course of schizophrenia-spectrum illness (original) (raw)
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Intellectual and cognitive profiles in patients affected by schizophrenia
Journal of neuropsychology, 2018
Intellectual abilities display high heterogeneity in patients with schizophrenia that might depend on the interaction among neurodevelopmental processes, environmental factors and neurocognitive decline. This study aimed to disentangle the interplay between intellectual level, cognitive status and each cognitive domain, with a focus on speed-related abilities, also including pre-morbid factors. In details, by means of cluster analysis, we identified both in global sample of 452 patients affected by schizophrenia and in a subsample with high pre-morbid functioning, different profiles based on current intellectual level and global cognitive status, analysing the distribution of deficits in each cognitive domains between groups. Then, through regression models, we analysed the contribution of speed-related domains and global cognitive profile to each other cognitive function. Considering the whole sample, results highlight three groups (high, medium and low cognitive level), while amon...
IQ and risk for schizophrenia: a population-based cohort study
Psychological Medicine, 1997
Background. This study aimed to quantify the association between low IQ and the later development of psychosis in a population-based cohort study of 18-year-old conscripts. Methods. Fifty thousand males conscripted into the Swedish army in 1969-1970 were followed by means of the Swedish National Register of Psychiatric Care up to 1983. Tests of verbal and visuospatial abilities, general and mechanical knowledge and several psychosocial variables were recorded at conscription. Results. One hundred and ninety-five subjects were admitted to hospital with schizophrenia and 192 with a non-schizophrenic psychosis on ICD-8 criteria. The distribution of scores in those later diagnosed as suffering from schizophrenia was shifted in a downward direction, with a linear relationship between low IQ and risk. This remained after adjustment for potential confounders. The risk for non-schizophrenic disorders was also higher in those with lower IQ but the effect was less marked and non-linear. Only poorer performance on the verbal tasks and mechanical knowledge test conferred a significantly increased risk for schizophrenia after taking into account general intellectual ability. Low IQ at conscription was not related to age of onset. Conclusions. The results confirm the importance of low intellectual ability as a risk factor for schizophrenia and other psychoses. This is unlikely to be due to prodromal decline or known confounders. The association could be directly causal with cognitive impairment leading to false beliefs and perceptions, or could be indirect with any factors causing lower IQ, such as abnormal brain development increasing the risk for schizophrenia.
European Child & Adolescent Psychiatry, 2010
Only few prospective longitudinal studies have assessed the course of intelligence deficits in early onset schizophrenia (EOS), and these have used different age appropriate versions of Wechsler Intelligence Scales and age appropriate norms. The post-psychotic development of intelligence in EOS has predominantly been characterized as relatively stable in these studies. However, comparisons of IQs from different test versions based on the different norms may not permit unequivocal interpretations. The objective of the current study was to compare the development of intelligence in EOS patients (N = 10) from their first psychotic episode to 5 years of post onset with that of healthy controls (N = 35) and patients who at baseline had been diagnosed with other non-affective psychoses (N = 8). The same version of a Wechsler Intelligence Scale was administered at both baseline and follow-up assessments, and the same norms were used to derive IQs at baseline and followup. Significantly smaller change in mean full scale intelligence quotient (FSIQ) was found in diagnostically stable EOS patients compared with healthy controls during the follow-up period. However, no statistically significant difference in mean FSIQ change was observed between patients with EOS and patients with other non-affective psychoses, although this result must be interpreted with caution due to the small sample sizes. The results suggest abnormally slow acquisition of new intellectual information and skills in EOS patients during the first 5 years after full clinical presentation.
Preserved, deteriorated, and premorbidly impaired patterns of intellectual ability in schizophrenia
Neuropsychology, 2014
Objective: The main purpose of this investigation was to identify patterns of intellectual performance in schizophrenia patients suggesting preserved, deteriorated, and premorbidly impaired ability, and to determine clinical, cognitive, and functional correlates of these patterns. Method: We assessed 101 patients with schizophrenia or schizoaffective disorder and 80 non-psychiatric control participants. The "preserved" performance pattern was defined by average-range estimated premorbid and current IQ with no evidence of decline (premorbid-current IQ difference Ͻ10 points). The "deteriorated" pattern was defined by a difference between estimated premorbid and current IQ estimates of 10 points or more. The premorbidly "impaired" pattern was defined by below average estimated premorbid and current IQ and no evidence of decline greater than 10 points. Preserved and deteriorated patterns in healthy controls were also identified and studied in comparison to patient findings. The groups were compared on demographic, neurocognitive, clinical and functionality variables. Results: Patients with the preserved pattern outperformed those meeting criteria for deteriorated and compromised intellectual ability on a composite measure of neurocognitive ability as well as in terms of functional competence. Patients demonstrating the deteriorated and compromised patterns were equivalent across all measures. However, "preserved" patients failed to show any advantage in terms of community functioning and demonstrated cognitive impairments relative to control participants. Conclusions: Our results suggest that proposed patterns of intellectual decline and stability exist in both the schizophrenia and general populations, but may not hold true across other cognitive abilities and do not translate into differential functional outcome.
Intelligence in Schizophrenia: Meta-analysis of the Research
Schizophrenia Bulletin, 1984
This article combines a review and meta-analysis of research on IQ in schizophrenia, with emphasis on areas of convergence in the findings, as well as questions that remain to be answered. Taken together, the findings suggest that early-onset and adult-onset schizophrenia are associated with intellectual deficits across the lifespan. Preschizophrenic children, adolescents, and young adults perform below matched controls on a variety of standardized measures of intelligence. Significant IQ deficits are also apparent after the onset of the disorder. Moreover, IQ is positively related to several indices of prognosis, and, among hospitalized patients, there is negative within-subject covariance between intellectual performance and symptom severity. Although there is fairly consistent evidence that Verbal IQ is higher than Performance IQ among schizophrenic patients, a more specific pattern of subtest performance is not apparent. A central question raised by the results is whether IQ is an independently determined factor that can serve to mitigate the vulnerability of individuals who are constitutionally predisposed to schizophrenia, or whether intellectual deficit is one manifestation of the constitutional predisposition to the disorder. The findings also raise the question of possible sex differences in the developmental determinants of schizophrenia: Meta-analyses revealed that premorbid IQ deficits are more prevalent among males than females.
Journal of Neuropsychiatry, 2005
Substantial research has demonstrated that adults with schizophrenia display intellectual decline compared to their premorbid levels of functioning. Research of this type, however, is not as common in adolescents with psychotic disorders. Since many first-episode adolescents with psychotic disorders other than schizophrenia may eventually meet criteria for this diagnosis, we examined first admission adolescents with variable psychiatric diagnoses. In this study, current intellectual functioning was compared to estimated premorbid functioning (estimated with word recognition reading), and the difference between these scores was related to the number of indicators of psychosis that was present in each case. Subjects consisted of 513 inpatients, ranging in age from 13 to 17 years, who were admitted to the adolescent service of a private psychiatric hospital. Indicators of psychosis came from clinical diagnoses, self-report measures, and clinical rating scales. Across the entire sample of 513 subjects the greater the number of indicators of psychosis that was present, the greater the estimated premorbid/current intelligence quotient (IQ) discrepancy. Type of IQ test, differences in intellectual premorbid functioning, demographic variables, and type of treatment were all unassociated with risk for IQ discrepancy. Within the limitations of estimation of premorbid intellectual functioning, these data suggest that intellectual decline is present at the time of the first psychiatric admission in psychotic adolescent patients who do not necessarily meet diagnostic criteria for schizophrenia and that this discrepancy is greater in patients with more indicators of psychosis.
Cognitive function in schizophrenia: insights from intelligence research
The British Journal of Psychiatry, 2013
Nearly 20 years of research has failed to elucidate a defining 'cognitive signature' of schizophrenia. Instead, the most replicated finding is of impairment in virtually every cognitive domain that differs between individuals in degree but not specificity. The now widely held view, that cognitive impairment in schizophrenia is generalised, and the observation that it is present at psychosis onset 2 and is more strongly correlated with functional outcomes than symptoms, 3 suggests that cognitive function should be introduced into clinical practice as an important dimension of the disorder. The growing recognition that there are psychological interventions that improve general cognition in schizophrenia 4 makes this a particularly timely and important consideration.
Course of intellectual functioning in schizophrenia and bipolar disorder: a 10-year follow-up study
Psychological Medicine, 2022
Background Intellectual functioning (IQ) is lower in schizophrenia patients compared to healthy controls, with bipolar patients intermediate between the two. Declines in IQ mark the onset of schizophrenia, while stability is generally found post-onset. There are to date few studies on long-term IQ development in bipolar disorder. This study presents 10-year follow-up data on IQ, including premorbid IQ estimates, to track the developmental course from pre-onset levels to long-term outcomes in both patient groups compared to healthy controls. Methods We included 139 participants with schizophrenia, 76 with bipolar disorder and 125 healthy controls. Mixed model analyses were used to estimate developmental slopes for IQ scores from estimated premorbid level (NART IQ) through baseline (WASI IQ) measured within 12 months post-onset, to 10-year follow-up (WASI IQ), with pairwise group comparisons. The best fit was found using a model with a breakpoint at baseline assessment. Results Only t...
Schizophrenia Research - SCHIZOPHR RES, 2006
Background: Some, but not most, schizophrenia patients have below-average intelligence years before they manifest psychosis. However, it is not clear if those whose intelligence falls within-normal-range nevertheless have cognitive abnormalities. We examined the association between intra-individual variability in intellectual performance and risk for schizophrenia in individuals with normal IQ. Methods: 555,326 adolescents, mandatory assessed by the Israeli Draft Board were followed up over 8 to 17 years for psychiatric hospitalization by means of the Israeli National Psychiatric Hospitalization Case Registry. Data were available on 4 intelligence sub-tests, and on behavioral and psychosocial variables. Variability was computed from the variance of the four intelligence tests' standardized scores. Results: There was a significant monotonic association between increased intra-individual variability in intellectual performance and risk of schizophrenia in individuals with within-normal-range IQ. Individuals with the highest variability were 3.8 times more likely to have schizophrenia [95%CI: 2.32-6.08; p b 0.0001] compared with individuals with the lowest variability. This association held after controlling for the effects of potential confounders. 0920-9964/$ -see front matter D (A. Reichenberg). Schizophrenia Research 85 (2006) 49 -57 www.elsevier.com/locate/schres
Premorbid IQ and adult schizophrenia spectrum disorder: Verbal Performance subtests
Psychiatry Research, 2010
The present prospective high-risk study examined associations between childhood scores on five Wechsler Intelligence Scale for Children (WISC) subtests (vocabulary, similarities, block design, object assembly, and mazes) and later development of schizophrenia spectrum disorders (SSD). The sample comprised 244 highrisk or control children who were administered the WISC subtests at age 10 to 13 years in 1972. Adult psychiatric data were gathered from psychiatric interviews in 1992-93 and from the Danish Psychiatric Central Register in 2007. Thirty-two participants had developed SSD, 79 other psychiatric disorders (OPD), and 133 had no diagnosis (ND). The SSD group obtained lower scores than the ND group on all subtests and IQs, but when adjusted for sex and parental social status only significantly lower scores on similarities, object assembly, mazes, and total IQ. Compared with the ND group, the OPD group obtained significantly lower scores on similarities, vocabulary, verbal IQ, and total IQ. The only significant difference between the SSD and OPD groups was on object assembly (OPD performed at the level of ND). The results suggest a premorbid deficit in general intelligence in individuals who later develop SSD. The results for the OPD group support recent studies demonstrating that premorbid IQ deficits may characterize a wide range of psychiatric disorders.