Elsevier

Psychiatry Research

Volume 266, August 2018, Pages 147-151
Psychiatry Research

Associations between olfactory identification and (social) cognitive functioning: A cross-sectional study in schizophrenia patients and healthy controls

https://doi.org/10.1016/j.psychres.2018.05.009Get rights and content

Highlights

  • In a large sample of schizophrenia patients and controls we assessed OI.

  • We are the first to comprehensively study multiple cognitive domains related to OI.

  • Worse OI was related to worse functioning on a range of (social) cognitive domains.

  • Worse OI was related to multiple measures of childhood/adolescent functioning.

  • These associations did not differ between schizophrenia patients and controls.

Abstract

Schizophrenia patients have difficulties identifying odors, possibly a marker of cognitive and social impairment. This study investigated olfactory identification (OI) differences between patients and controls, related to cognitive and social functioning in childhood and adolescence, to present state cognition and to present state social cognition. 132 schizophrenia patients and 128 healthy controls were assessed on OI performance with the Sniffin’ Sticks task. Multiple regression analyses were conducted investigating OI in association with cognitive and social functioning measures in childhood/adolescence and in association with IQ, memory, processing speed, attention, executive functioning, face recognition, emotion recognition and theory of mind. Patients had reduced OI performance compared to controls. Also, patients scored worse on childhood/adolescence cognitive and social functioning, on present state cognitive functioning and present state social cognition compared to controls. OI in patients and controls was significantly related to cognitive and social functioning in childhood/adolescence, to present state cognition and to present state social cognition, with worse functioning being associated with worse OI. In this study, findings of worse OI in patients relative to controls were replicated. We also showed associations between OI and cognitive and social functioning which are not specific to schizophrenia.

Introduction

Schizophrenia patients have difficulties identifying odors (Moberg et al., 2014). The degree of this reduced odor identification (OI) compared to healthy controls has been examined extensively. A meta-analysis by Cohen et al. (2012) showed that OI in schizophrenia is nearly a standard deviation below the mean of controls.

Schizophrenia is also characterized by cognitive and social cognitive deficits, particularly in IQ, memory, processing speed, attention, executive functioning, emotion recognition and theory of mind (Mesholam-Gately et al., 2009). These deficits appear to be present before illness onset, as previous birth cohort studies showed that on average, subjects who later develop schizophrenia report poorer cognitive and social functioning in childhood and adolescence (Welham et al., 2009). Interestingly, impairments in social behavior and social cognition (i.e. emotion recognition) in schizophrenia have been related to OI deficit (Malaspina and Coleman, 2003, Kohler et al., 2007 resp.). Furthermore, previous studies have shown that OI and cognition are positively associated in schizophrenia (Brewer et al., 1996, Compton et al., 2006, Good et al., 2002, Goudsmit et al., 2004, Malaspina and Coleman, 2003, Moberg et al., 2006, Purdon, 1998, Saoud et al., 1998, Seckinger et al., 2004, Seidman et al., 1997, Seidman et al., 1991, Stedman and Clair, 1998) and in controls (Brewer et al., 1996, Compton et al., 2006, Seidman et al., 1991), with moderate strength in both groups. However, in the majority of these studies only one or two cognitive domains were examined in relation to OI and often a range of possible confounders such as age, gender, smoking and the use of antipsychotics associated with OI (Moberg et al., 2014) was not taken into account. Moreover, most studies lacked a control group.

Olfactory development is dependent on the development of frontal and temporal lobe areas (Nguyen et al., 2010, Turetsky et al., 2009) and its cognitive (i.e. IQ, memory, processing speed, attention, executive functioning) and social cognitive related functioning (Aleman, 2014). Since cognitive and social functioning in childhood and adolescence is already dependent on the brain maturation of these areas early in life we expect a relationship between OI and cognitive and social functioning in childhood and adolescence. To date, no studies have been performed linking OI to cognitive and social functioning in childhood and adolescence and to present state functioning on multiple social cognitive domains. In this study we therefore comprehensively examine whether OI is related to cognitive and social functioning in childhood and adolescent, as well as to a range of present state social cognitive domains in a large sample of schizophrenia patients and healthy controls. Furthermore, we aim to replicate whether olfactory functioning is associated with present state cognition.

Section snippets

Study design and population

Data from this cross-sectional study pertain to the multicenter ‘Genetic Risk and Outcome in Psychosis’- project (GROUP). This trial was part of an add-on study during the second measurement of this Dutch longitudinal GROUP–project. Participants were assessed extensively and were invited to participate in diagnostic interviews, questionnaires and neuropsychological tasks. The study protocol was approved by the accredited Medical Ethics Review Committee. All participants signed informed consent.

Sample characteristics

Table 1 summarizes socio-demographic differences between patients and controls. Clinical characteristics of patients are also summarized in Table 1. OI, cognitive and social functioning in childhood/adolescence, present state cognition and present state social cognition were significantly lower in patients compared to controls (see Table 2). Lower OI performance in patients compared to controls remained significant after correcting for gender, age, APD use and smoking. The R2 did not change

Discussion

In the largest group of schizophrenia patients (n = 132) and healthy controls (n = 128) up to date, we examined OI in relation to childhood and adolescent cognitive and social functioning as well as present state cognition and social cognition. The most original and novel finding of our study is that social and cognitive functioning in childhood/adolescence and present state social cognition domains of theory of mind and face recognition are related to OI.

We found that reduced OI was related to

Conflict of interest

Lieuwe de Haan has received research funding form Eli Lilly and honoraria for educational programs from Eli Lilly, Jansen Cilag, BMS, Astra Zeneca. Rene S. Kahn is or has been a member of DSMB for Janssen, Otsuka, Sunovion and Roche. Wiepke Cahn is or has been an unrestricted research grant holder with, or has received financial compensation as an independent symposium speaker or as a consultant from Eli Lilly, BMS, Lundbeck, Sanofi-Aventis, Janssen-Cilag, AstraZeneca and Schering-Plough. All

Funding

The infrastructure for the GROUP study is funded through the Geestkracht programme of the Dutch Health Research Council (ZON–MW, grant number 10–000–1001). The funders had no role in study design, data collection and analysis, decision to publish or preparation of the manuscript.

Acknowledgment

We are grateful for the generosity of time and effort by the participants and their families, healthy subjects, and all researchers who make this GROUP–project possible.

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