Premorbid IQ and schizophrenia (original) (raw)
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Population-based Cohort Studies on Premorbid Cognitive Function in Schizophrenia
Epidemiologic Reviews, 2008
Many previous studies have found associations between poor cognitive function and schizophrenia. However, the majority of these studies used retrospective data, leading to the possibility of selection and recall biases. Retrospective studies are also unable to distinguish whether cognitive deficits exist prior to the onset of schizophrenia, suggesting that they are important in etiology, or following onset, suggesting that they are secondary to the disorder or its treatment. The current review used a systematic search strategy to identify and summarize the results of all studies that have used population-based cohorts to examine associations between prospectively collected data on premorbid cognitive functioning in childhood or adolescence and subsequent risk for schizophrenia. Three broad categories of study have addressed these questions: birth cohort designs with cognitive testing during childhood, army conscript designs with cognitive performance measured at conscription, and studies using school grades. Birth cohort and conscript studies are consistent in reporting strong associations between poor performance on cognitive batteries and increased risk of schizophrenia. Studies on school performance have been less consistent, although the largest such study showed strong associations across all school subjects. In conclusion, children and adolescents with poor cognitive abilities in childhood are at increased risk of schizophrenia. This suggests that poor cognitive function is either directly causal or associated with causal factors that are involved in etiology. adolescent development; child development; cohort studies; intelligence; learning disorders; review; schizophrenia Abbreviation: IQ, intelligence quotient.
Schizophrenia Research: Cognition, 2015
Neurocognitive dysfunction is common in schizophrenia but its course and determinants remain uncertain. Our aim was to analyse if premorbid school performance and the severity of illness and functioning predict change in cognition in schizophrenia in a general population sample. The sample included cases with schizophrenia spectrum disorder from the Northern Finland Birth Cohort 1966. Data on school marks at the age of 16 years, educational level at the age of 34 years, severity of symptoms and occupational functioning around first episode and after years of illness were gained from national registers, hospital notes and interviews. Change of verbal and visual learning and memory and executive functioning were examined between ages 34 and 43 years. The number of cases varied in analyses from 29 to 41, depending on missing data in particular cognitive tests. Lower school marks at age 16 years and lower education at age 34 years predicted more decline of cognition. Measures of severity of illness or functioning were not associated statistically significantly with change of cognition. Premorbid school performance, but not later course of schizophrenia, related to change of cognition in midlife. Poor premorbid scholastic performance and post-onset cognitive decline may represent related processes as part of an endophenotype of schizophrenia.
Schizophrenia Research, 2007
Introduction: Approximately one third of schizophrenia patients show partial or no response to pharmacotherapy. Despite intensive investigations, the phenomenological and biological characteristics of such patients are far from elucidated. This study examined the premorbid behavioral and intellectual functioning of schizophrenia patients who showed poor response to antipsychotic treatment. Method: One hundred twenty-nine schizophrenia patients who showed poor response to treatment were ascertained from a national register and matched by gender, age and education to 129 patients who showed adequate response. The groups were compared on premorbid measures of behavioral and intellectual functions. Results: As a group, treatment-resistant male patients had significantly lower (worse) social functioning [p = 0.002], and individual autonomy [p b 0.0001] scores before the onset of the illness compared to treatment non-resistant patients. Male and female treatment-resistant patients did not differ from non-resistant patients in premorbid intellectual functioning [p N 0.1]. Conclusions: Low premorbid social functioning and individual autonomy, but not intellectual functioning, could serve as predictors of poor treatment response in schizophrenia.
Cognitive dysfunctions in medicated and unmedicated patients with recent-onset schizophrenia
Journal of Psychiatric Research, 2005
Schizophrenia is associated with impairments in many cognitive domains on which the influence of antipsychotics, whether conventional or atypical, remains unclear. We conducted a study of recent-onset schizophrenic patients (DSM IV) that included unmedicated (n = 19), and medicated (n = 19) patients matched for age and IQ. Both groups of patients had comparably low extra-pyramidal symptoms (EPS). Cognitive tasks included attentional tasks (alertness and divided attention tests), a working memory task (a verbal n-back test) and the Wisconsin Card Sorting Test (WCST). After adjustment for the Total PANSS score, we found no significant difference between the two groups of patients in any of the cognitive tasks. When compared to a group of healthy controls (n = 20) matched for IQ level, unmedicated patients performed significantly worse in all cognitive tasks, with significantly longer reaction times for alertness, divided attention and working memory. These results confirm the presence of cognitive impairments in attentional and executive functions in recent-onset patients whether or not they are medicated. There was no evidence that either conventional or atypical antipsychotics had an influence on patients when EPS were excluded. Altogether, our results further support the idea that cognitive deficits in schizophrenia are enduring features per se and cannot be considered as secondary to psychiatric symptoms or to the adverse effects of medication. In addition our results suggest that antipsychotics do not have a major effect on these impairments.
Longitudinal study of cognitive function in first-episode and recent-onset schizophrenia
The American journal of psychiatry, 1999
OBJECTIVE Whether cognitive function in schizophrenia deteriorates, improves, or remains stable is a crucial question. Few studies have examined the longitudinal stability of cognitive function and the relationship between cognitive performance and clinical symptoms over time in a cohort of well-treated patients with schizophrenia. METHOD In the present study, 54 patients with first-episode and recent-onset schizophrenia completed a comprehensive cognitive test battery and were rated on symptom measures at index hospitalization and again after 5 years. RESULTS Performance IQ and full-scale IQ significantly improved, whereas verbal IQ did not change. Group performance improved on some of the neuropsychological tests, including the Circle A letter-cancellation task, free recall of logical memory test score, and the Wisconsin Card Sorting Test. Mean finger-tapping performance worsened over time, whereas performance on other neuropsychological tests did not change. Negative, psychotic, ...
The Early Longitudinal Course of Cognitive Deficits in Schizophrenia
The Journal of Clinical Psychiatry, 2014
Cognitive impairment is a core feature of schizophrenia. However, the longitudinal course and pattern of this impairment, and its relationship to functional outcome, are not fully understood. Among the likely factors in the persistence of cognitive deficits in schizophrenia are brain tissue changes over time, which in turn appear to be related to antipsychotic medication adherence. Cognitive deficits are viewed as a core feature of schizophrenia primarily because cognitive deficits clearly exist before the onset of psychosis and can predict illness onset among those at high risk of developing the illness. Additionally, these deficits often persist during symptomatic remissions in patients and are relatively stable across time both in patients and in individuals at risk for schizophrenia. Despite clear evidence that cognitive impairment can predict functional outcome in chronic schizophrenia, results of studies examining this relationship in the early phase of psychosis have been mixed. Recent data, however, strongly suggest that interventions targeting early cognitive deficits may be crucial to the prevention of chronic disability and thus should be a prominent target for therapy. Finally, it is vital to keep schizophrenia patients consistently on their antipsychotic medications. A novel method of examining intracortical myelin volume indicated that the choice of antipsychotic treatment had a differential impact on frontal myelination. These data suggest that long-acting injectable antipsychotic medication may prevent patients from declining further through a combination of better adherence and pharmacokinetics.
The Maudsley Early Onset Schizophrenia Study: Cognitive Function Over a 4-Year Follow-Up Period
Schizophrenia Bulletin, 2007
Generalized cognitive deficits have been consistently reported in adolescents with early onset schizophrenia (EOS; defined as onset before the age of 17 years). The impact on cognition of potential interactions between disease pathology and brain maturation remains unclear. We therefore compared cognitive function between 20 EOS patients and 20 healthy controls matched on age, gender, and parental socioeconomic status at 2 time points, when aged 15.58 (2.27) and after a mean interval of 4 6 1.08 years when aged 19.46 (2.21) years. Repeated measures analyses revealed no differences between patients and controls in the degree of change over this time period in general intellectual function and planning ability as measured by the Tower of London. There was deterioration in the verbal memory and attentional control index scores from the Wechsler Memory Scale-Revised but relative improvement in Part A of the Trail Making Test. Patients' level of symptomatology as well as the type and dose of medication were comparable at both time points. We conclude that most aspects of cognitive function remain relatively stable in EOS patients during adolescence; there is evidence for deterioration in immediate verbal memory and attention while speed of information processing may show improvement.