A Swedish National Prospective and Co-relative Study of School Achievement at Age 16, and Risk for Schizophrenia, Other Nonaffective Psychosis, and Bipolar Illness

Abstract

While cognitive ability is inversely associated with risk for schizophrenia (SZ), the association is less clear with other nonaffective psychoses (ONAP) and bipolar illness (BPI). Using national Swedish hospital registry dataThe association between SA and risk was stronger in the lower vs the higher ranges of SA. In most analyses, moderate increases in risk were observed at the highest levels of SA, with the strongest evidence for females and risk of ONAP. Co-relative control analyses indicated that common genetic or familial-environmental effects only marginally confounded these associations. Consistent with prior studies, these results have 3 major implications for neurodevelopmental models: (1) adolescent cognitive deficits that increase risk are not the result of prodromal changes,( 2) individual specific environmental exposures are largely responsible for the association between low SA and psychosis risk, and (3) neurodevelopmental disturbances (as indicated by low SA) are not unique to SZ but also occur in ONAP and to a lesser degree BPI.Key words: Cognitive ability/school performance/ schizophrenia/bipolar illness/other nonaffective psychoses/prospective risk/co-relative control analysis A series of meta-analyses have convincingly shown that cognitive ability is inversely related to risk for future schizophrenia (SZ) onsets 1-4 although a question remains whether this relationship holds at the highest levels of cognitive performance. 3,5,6 The association between cognitive functioning and risk for bipolar illness (BPI) is less consistent, 7-10 with some evidence that higher cognitive functioning is associated with elevated risk. 10,11 The relationship between cognitive performance and risk for other nonaffective psychosis (ONAP) has been less studied but extant research suggests that it resembles the relationship seen for SZ. 9,12 In our prior study of cognitive ability indexed by IQ, IQ obtained at military conscription at age 18-20 had a strong and monotonic inverse relationship with risk for onset of SZ in Swedish males.6 Co-relative analyses suggested that the IQ-SZ relationship was not due to genetic or environmental familial risk factors that predisposed both to low IQ and SZ. While some prior reports, including a Finnish longitudinal study, found enrichment for cases of SZ among those with the highest level of cognitive functioning (indicating an inverted J-shaped relationship between performance and SZ risk), 3,5 we found no evidence that high IQ is associated with increased risk for SZ. However, our study was unable to investigate this relationship at the highest end of the IQ distribution because the highest performing group in our study had a mean IQ of 129, slightly less than 2 standard deviations above the mean.In the present study, we had access to a measure of aggregate school achievement (SA) at age 16 in a nearly complete sample of native Swedish children of both sexes born between 1972 and 1990 (n = 1 800 643). While substantially correlated, SA is not identical to IQ and has Downloaded ...

Cognitive Deficits in Psychotic Disorders: A Lifespan Perspective

“…Even among the studies finding premorbid cognitive impairments in bipolar disorder with psychotic features, these impairments are generally less severe than found in premorbid schizophrenia (Daban et al 2006; Seidman et al 2013; Kendler et al 2016). Although schizophrenia is associated with greater premorbid IQ deficits than bipolar disorder in several studies (Simonsen et al 2011; Zanelli et al 2010), others have failed to find this association (Olvet et al 2010; Seidman et al 2002).…”

“…This is approximately half of the deficit seen in first-episode and chronic schizophrenia patients (Reichenberg and Harvey 2007). In terms of the relationship between premorbid school achievement and schizophrenia, poor premorbid school performance is generally associated with increased risk for schizophrenia (Crow et al 1995; Fuller et al 2002; Kendler et al 2016; MacCabe et al 2008; Strauss et al 2012; Watt and Lubensky 1976). However, one meta-analysis found that children who later develop schizophrenia do not show deficits in premorbid academic performance (Dickson et al 2012), and other research has pointed to intact early school functioning but later difficulties in schooling that are associated with severity of symptoms (Helling et al 2003) and poorer outcomes (Cannon et al 1999; Ang and Tan 2004).…”

The Protective Effect of Pregnancy on Risk for Drug Abuse: A Population, Co-Relative, Co-Spouse, and Within-Individual Analysis

“…Model 1 was only a crude model, whereas in model 2 we adjusted for mid-parent educational status [(1) <=9 years, (2) 10–11 years, (3) 12 years or more] and school achievement (SA) of the individual (see (25) for a definition of SA).…”

Tobacco use and psychosis risk in persons at clinical high risk

“…Initiation of smoking occurs before psychosis symptoms emerge for about 75% of persons with schizophrenia (de Leon & Diaz, 2005), and prospective population-based cohort studies (Kendler, Lonn, Sundquist, & Sundquist, 2015;Riala, Hakko, Isohanni, Pouta, & Rasanen, 2005;Sorensen, Mortensen, Reinisch, & Mednick, 2011;Weiser et al, 2004;Zammit et al, 2003) find that risk of schizophrenia is about doubled for tobacco smokers (Gurillo et al, 2015). Based on the observed temporal precedence and that higher levels of tobacco use are associated with higher risk of subsequent schizophrenia (Kendler et al, 2015;Weiser et al, 2004), several researchers propose that there is a causal relationship between smoking tobacco and the development of a psychotic disorder (Alderson & Lawrie, 2015;Gage & Munafo, 2015;Gurillo et al, 2015;Kendler, Ohlsson, Mezuk, Sundquist, & Sundquist, 2016;Wium-Andersen, Orsted, & Nordestgaard, 2015).…”

“…These same investigators (Alderson & Lawrie, 2015, Gage & Munafo, 2015, Gurillo et al, 2015, Kendler et al, 2016, Wium-Andersen et al, 2015 acknowledge, however, the many challenges to establishing causality in observational studies, especially that of confounding. Factors associated with increased risk of smoking initiation and dependence in the general population, if also associated with psychosis risk, could confound associations of smoking and schizophrenia.…”