Precursors of cognitive impairments in psychotic disorders: A population-based study

Abstract

Cognitive deficits have been found to be more prevalent in psychotic than in other disorders. Longitudinal research has shown that these deficits were generally already existent before onset of illness and are therefore not necessarily attributable to neurodegenerative processes. This study investigated whether both low IQ and markers of premorbid cognitive dysfunction independently contribute to an increased risk for psychoses. In a cross-sectional study about 50,000 young Swiss males completed a survey of intellectual problems in childhood/adolescence and other vulnerability factors during military call-up in 2005/2006. Subsequently, military IQ assessments were carried out on the entire sample. Diagnostic assessments were conducted according to International Classification of Diseases-10th edition (ICD-10). Low, especially performance, IQ was highly associated with an increased risk for psychotic disorders after adjusting for preexisting cognitive deficits and covariates, while in other disorders this association was less marked. Furthermore, preexisting intellectual problems emerged as important risk factors for psychoses. Our results confirm the importance of low IQ as characteristic of psychoses. Although premorbid intellectual deficits are common in people who go on to develop psychosis, neurodegenerative disease processes may also precipitate further declines in fluid cognitive functions. Assessment of cognitive functioning should be taken into account in early detection of psychoses. Longitudinal research has shown that these deficits were generally already existent before onset of illness and are therefore not necessarily attributable to neurodegenerative processes. This study investigated whether both low IQ and markers of premorbid cognitive dysfunction independently contribute to an increased risk for psychoses. In a cross-sectional study about Subsequently, military IQ assessments were carried out on the entire sample. Diagnostic assessments were conducted according to ICD-10. Low, especially performance IQ was highly associated with an increased risk for psychotic disorders after adjusting for preexisting cognitive deficits and covariates; while in other disorders this association was less marked.Furthermore, preexisting intellectual problems emerged as important risk factors for psychoses.Our results confirm the importance of low IQ as characteristic of psychoses. Although premorbid intellectual deficits are common in people who go on to develop psychosis, neurodegenerative disease processes may also precipitate further declines in fluid cognitive functions. Assessment of cognitive functioning should be taken into account in early detection of psychoses.

Changes in neurocognitive functioning during transition to manifest disease: comparison of individuals at risk for schizophrenic and bipolar affective psychoses

“…During baseline testing, our sample group of 'true' at-risk individuals with later conversion was exhibiting significantly lower performances on the domains of processing speed, fluency, learning/memory, and working memory, as well as a lower estimated pre-morbid IQ. Thus, our results may confirm the assumption that neurocognitive deficits are present prior to the development of psychosis Giuliano et al 2012;Fusar-Poli et al 2012a;Müller et al 2013;Bora et al 2014).…”

“…Some researchers have critically questioned whether schizophrenia is inherently progressive and have suggested that the disability may result -unless referral and sampling biases exist -from stable deficits that are established before the onset of the illness Bora & Murray, 2013;Zipursky et al 2013). In line with a neurodevelopmental model of schizophrenia, recent studies have provided evidence that cognitive and intellectual deficits are apparent early in neurodevelopment, several years before the onset of psychosis Giuliano et al 2012;Fusar-Poli et al 2012a;Müller et al 2013;Bora et al 2014). Birth cohort and conscript studies report strong associations between poor performance on cognitive batteries and increased risk of later schizophrenia (MacCabe, 2008;MacCabe et al 2008).…”

Neurocognitive profiles in help-seeking individuals: comparison of risk for psychosis and bipolar disorder criteria

“…According to the neurodevelopmental hypothesis of pathogenesis in schizophrenia, along with recent findings, neurocognitive deficits are most likely to be present prior to the manifestation of full-blown schizophrenia (Giuliano et al 2012). This supposition is also supported by a recent large population study of young Swiss conscripts by Müller et al (2013), who found significantly frequent evidence of cognitive impairments early in life for individuals who were later diagnosed with schizophrenia. Therefore, an assessment of cognitive functioning should be taken into account in early detection of psychoses.…”

Association between processing speed and subclinical psychotic symptoms in the general population: Focusing on sex differences

“…Various ensuing studies replicated those cognitive deficits prior to the onset of full-blown psychosis (e.g., MacCabe et al, 2008;MacCabe et al, 2013;Metzler et al, 2014;Müller et al, 2013;Reichenberg et al, 2010;Zammit et al, 2004). Broad scientific consensus now exists among experts that poor premorbid cognitive functioning is a risk factor for schizophrenia and other psychotic disorders (Khandaker et al, 2011;MacCabe, 2008).…”

“…We are unaware of further reports about cognitive deficits that are separated by sex in those phenotypes. Many conclusions about premorbid cognitive functioning in psychosis have been drawn exclusively from male samples (e.g., MacCabe et al, 2013;Müller et al, 2013;Zammit et al, 2004). None of the studies focusing on the extended psychosis phenotype have examined potential sex differences.…”