General intellectual functioning as a buffer against theory-of-mind deficits in individuals at ultra-high risk for psychosis

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Abstract

The influence of neurocognition, including general intelligence, on theory of mind (ToM) among patients with schizophrenia spectrum disorder is controversial. The purpose of the present study was to identify the influences of the non-ToM cognition and general intelligence on ToM performance in individuals at ultra-high risk (UHR) for psychosis. Fifty-five UHR subjects and 58 healthy controls (HCs) completed neurocognitive, verbal, and nonverbal ToM tasks. UHR individuals showed poorer performance in the two verbal ToM tasks, the false-belief task and the strange-story tasks. Moreover, the UHR subjects displayed poorer recall on the interference list of the verbal learning test. Linear regression analysis revealed that neurocognitive functioning, including executive functioning, working memory, and general intelligence, accounted for significant amounts of the variance in the results for UHR individuals: 20.4% in the false-belief task, 44.0% in the strange-story task, and 49.0% in the nonverbal cartoon task. Neurocognition, including general intelligence, was not a significant contributor to performance on ToM tasks in HCs. ToM deficits were not noted in UHR individuals with above-average IQ scores (≥ 110) compared with UHR subjects with IQ scores less than 110, who displayed significant differences on all ToM tasks compared with HCs. The present results suggest that ToM deficits in UHR individuals are complex and may be influenced by non-ToM cognition. Our findings are discussed in relation to the role of neurocognitive abilities in ToM-related impairments in UHR individuals.

Introduction

Theory of mind (ToM) is the mentalizing capacity to infer the mental state of others, including their thoughts, desires, and intentions, after establishing a reasonable conception of one's own mind (Frith, 1992, Abu-Akel, 2003). ToM dysfunction has been studied in patients with psychiatric and autism spectrum disorders. Deficits in ToM may underlie some of the issues associated with difficulties in daily functioning and predict the prognosis in certain patient groups (Baron-Cohen, 1989, Frith and Corcoran, 1996, Bora et al., 2009a, Gooding and Pflum, 2011). The nature of ToM impairments as well as the factors that likely affect ToM have been the focus of previous studies (Langdon et al., 2005).

Several recent studies in patients with schizophrenia (SZ) have examined whether non-ToM cognition and/or general intelligence affects ToM impairment. Previous research has suggested that cognition, including IQ, is not associated with impairment in ToM (Harrington et al., 2005, Inoue et al., 2006, Sprong et al., 2007, Mo et al., 2008). However, other studies (Pickup, 2008, Bora et al., 2009b) have suggested the possible correlations among IQ, executive functioning, memory, and ToM performance in patients with SZ. Moreover, deficits in ToM are neither consistent states nor independent traits in SZ samples (Brüne, 2003). For example, one research group reported that they did not find the ToM deficit in SZ after correcting for IQ (Pentaraki et al., 2008). Furthermore, working-memory deficits may explain ToM impairment in symptom-free patients (Bora et al., 2008). A meta-analysis also noted that the significant effect of IQ on ToM is present only in the individuals who have experienced remission from schizophrenia (Bora et al., 2009b). Therefore, the influence of IQ on ToM deficits may differ when symptoms are more stable, as when remission is achieved (Ventura et al., 2013).

ToM abilities are significant predictors of social adjustment and transition to psychosis (Chung et al., 2008, Stanford et al., 2011). Moreover, since the social cognition and neurocognition are meaningful in terms of the general functioning and prognosis of individuals with psychotic disorders (Gard et al., 2009, Couture et al., 2011), research on the link between neurocognition and social cognition in UHR subjects may offer significant insights to the clinical groups. Thus, the present study used a linear regression model to determine the contribution of non-ToM cognition and intellectual functioning on the ToM ability of UHR individuals. Despite the increasing evidence for IQ-independent ToM deficits in individuals with autism spectrum and bipolar disorders (Ozonoff et al., 1991, Baron-Cohen et al., 1997, Kerr et al., 2003, Inoue et al., 2004), very little research has linked ToM and non-ToM cognition.

In the present study, we assessed verbal and nonverbal ToM tasks, general intelligence, and non-ToM cognition. We aimed to investigate the influence of the non-ToM cognitive abilities on the ToM performances using the linear regression analyses. In light of previous findings, we hypothesized that UHR individuals would utilize non-ToM cognitive abilities when performing ToM tasks.

Section snippets

Participants

Fifty-five UHR participants were recruited from the Seoul Youth Clinic according to the Comprehensive Assessment of At-Risk Mental States (CAARMS) criteria (Yung et al., 2005) between April 2005 and July 2010. The UHR subjects were included if the individual met 1 or more of 3 well-operated and validated criteria. The UHR group were those with attenuated psychotic symptoms (n = 52) and/or trait-plus-state risk factors (n = 8). Five subjects met criteria for both attenuated psychotic symptoms and

Demographic and clinical characteristics

The demographic and clinical characteristics of the subjects are presented in Table 1. The UHR and HC groups did not differ with respect to age, sex or IQ (all Ps > 0.05). The mean duration of symptoms for individuals in the UHR group was 2.62 ± 2.39 years, and all individuals in this group were characterized by psychiatric symptoms according to the PANSS (Table 1).

Neurocognitive assessments

The MANOVA revealed significant group differences in the neurocognitive domain based (Wilks' λ = .80; F[1,111] = 2.51; P = .010). The UHR

Discussion

The aim of the present study was to examine whether the non-ToM cognition, including general intelligence, influence the performance on ToM-related tasks in individuals at UHR for psychosis. In this study, UHR subjects performed worse on verbal ToM tasks and non-ToM cognitive tasks, including those involving attention, executive functioning, and strength and management of working memory. Moreover, the CVLT index of verbal working memory which requires the freedom from previous distractive

Role of funding source

This study was supported by a grant of the Korean Health Technology R&D Project, Ministry of Health & Welfare, Republic of Korea (A120476).

Contributors

Ji-Won Hur undertook the study design and wrote the draft of the manuscript and administered neurocognitive tasks to the subjects who participated in this study. Min Soo Byun completed a screening interview for the subjects and gave advice throughout the study. Na Young Shin and Ye Seul Shin administered neurocognitive tasks to the subjects who participated in this study. Sung Nyun Kim and Joon Hwan Jang completed a screening interview for the subjects of this study. Jun Soo Kwon undertook the

Conflict of interest

None of the authors have any conflicts of interests to this study.

Acknowledgements

None.

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