Edited by: Thomas W. Weickert, University of New South Wales, Australia
Reviewed by: Assen Veniaminov Jablensky, The University of Western Australia, Australia; Marc Seal, Murdoch Childrens Research Institute, Australia; Cali Bartholomeusz, The University of Melbourne, Australia
Specialty section: This article was submitted to Schizophrenia, a section of the journal Frontiers in Psychiatry
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Previous research has shown mild forms of the neurocognitive impairments seen in schizophrenia among healthy individuals exhibiting high schizotypal traits. This study aimed to explore associations between schizotypy and cognitive performance in an adult community sample. Ninety-five females and 79 males completed the Oxford–Liverpool Inventory of Feelings and Experiences (O-LIFE), which measures four separable aspects of schizotypy: cognitive disorganization, unusual experiences, introvertive anhedonia, and impulsive non-conformity. Subsequently, participants were administered a neurocognitive battery incorporating measures of executive skills including inhibition, cognitive flexibility, reasoning, and problem solving along with measures of attention and processing speed and both verbal and spatial working memory. In line with predictions, the current study found that higher scores on the subscales of unusual experiences, cognitive disorganization, and impulsive non-conformity related to worse performance on a measure of inhibition. Additionally, as introvertive anhedonia increased, both attention and processing speed and reasoning and problem-solving performance became more impaired. In conclusion, this study extends schizotypy literature by examining the subscales of the O-LIFE, and enables inferences to be drawn in relation to cognitive impairment in schizophrenia.
Schizophrenia generally a lifelong psychiatric illness associated with distressing mood, cognitive, and functional symptoms (
Mild forms of the cognitive deficits observed in schizophrenia are also found in unaffected first-degree relatives and healthy individuals exhibiting schizotypal traits (
Positive schizotypy taps into perceptual aberrations, magical thinking, unusual experiences, and hallucinations, and is thought to resemble positive symptomatology in schizophrenia (
Poorer neurocognitive performance similar to that seen in schizophrenia, albeit in a milder form, has been identified in individuals exhibiting high levels of schizotypy traits (
Additionally, further evidence for poorer performance in attention and executive functioning has been identified by past research. Using the O-LIFE in a university sample, Rawlings and Goldberg (
Relative deficits in verbal and spatial working memory have also been identified by previous research. For instance, using a university sample, Matheson and Langdon (
Only a small number of studies have examined cognitive functioning in relation to separate schizotypy factors. These studies suggest that lowered performance in attention, executive functioning, and sustained attention (using a Continuous Performance Task) is related to higher scores on the cognitive disorganization schizotypy factor as well as negative schizotypy (
Taken together, these findings suggest that high schizotypy is associated with reduced cognitive ability (albeit milder than that seen in schizophrenia). However, this is a very broad finding and more fine-grained analysis of the nature of this relationship is required. As discussed, there are currently only a small number of articles examining the schizotypy subtypes (
Based on shortcomings in the literature, the current study aimed to explore the relationship between the four-schizotypy factors defined in the O-LIFE and those areas of cognition, which have previously been found to relate to schizotypy (inhibition, cognitive flexibility, attention, processing speed, and reasoning and problem solving) using traditional neurocognitive tasks. This study will address previous limitations by (a) looking at the relationship between individual schizotypy factors of the O-LIFE and cognition, (b) using a large sample, (c) over the typical age for schizophrenia onset, and (d) free from genetic liability and current psychopathology.
Given previous findings of inhibitory deficits in schizophrenia patients and high schizotypy samples, it was hypothesized that higher scores on the unusual experiences and cognitive disorganization factors of the O-LIFE would relate to poorer inhibition and cognitive flexibility, as measured by the Color–Word Interference Test performance. Additionally, in line with previous schizotypy literature, it was predicted that the introvertive anhedonia factor of the O-LIFE would negatively associate with reduced attention and processing speed, as measured by the Trail Making Test – Part A. Furthermore, it was hypothesized that there would be a negative association between the unusual experiences, introvertive anhedonia and impulsive non-conformity factors, and reasoning and problem-solving performance, as measured by a Mazes task. Lastly, based on previous findings in working memory and schizotypy, a negative relationship was also expected between both the unusual experiences and introvertive anhedonia factors, and verbal and spatial working memory performance, as measured by the Letter–Number Sequencing and Spatial Span Tasks. Furthermore, exploratory analyses of the four-schizotypy factors and all neurocognitive variables will be conducted.
Potential participants voluntarily responded to advertising through flyers at local community centers and the researcher’s private social media pages. Following telephone screening, 175 healthy adults between 18 and 64 years of age (95 women and 79 men) met participation inclusion criteria. Participants were excluded from the study if they had a current psychiatric illness; history of or first-degree biological relative with schizophrenia or schizoaffective disorder; current use of a psychotropic drug; or, history of substance abuse or neurological illness. Demographic information revealed that one included participant was adopted (hence, knowledge of their biological relatives’ psychiatric history was unknown), and one participant was color blind. The participant who was color blind was excluded from all color–word interference tasks. All participants were financially reimbursed for their time and travel costs. The Alfred Health Human Ethics Committee and the Monash University Standing Committee on Ethics in Research in Humans approved all experimental procedures and informed written consent was obtained by all participants in accordance with these ethical requirements.
For this study, the four variables of interest were: Inhibition V Color Naming raw time, which was a measure of inhibitory latency, once baseline color naming was controlled for by subtracting the raw seconds required for the first condition from the third condition; Inhibition/Switching V Inhibition raw time that was a score of cognitive flexibility or attentional switching, after inhibition was controlled for by subtracting the seconds score of the third condition from the fourth condition; Inhibition/Switching V Color Naming raw time, which was a measure of inhibitory latency and cognitive flexibility, once color naming was controlled for by subtracting the seconds required for the first condition from the fourth condition; and Inhibition/Switching V Word Reading raw time that was a measure of inhibitory latency and cognitive flexibility, after baseline wording reading was controlled for by subtracting the seconds taken for the second condition from the fourth condition.
Following a basic telephone assessment of eligibility, participants completed a demographic questionnaire and the O-LIFE. Subsequently, a brief screening interview took place, consisting of the M.I.N.I. screen and the MADRS. The neurocognitive battery was then administered successively, with counterbalancing used to reduce order effects and fatigue.
All raw scores were processed using PASW Version 18 (SPSS Ltd.) to produce the summary data. Although statistical analyses were based on previous literature, due to multiple comparisons, the alpha level for all statistical analyses was set at 0.01, unless otherwise stated.
Prior to analyses, assumption testing was conducted to assess the suitability of the data for a correlation analysis. Following inspection of the Frequency Table, it was found that a small percentage of data was missing from each of the variables (<5% per variable); cases were therefore excluded pairwise for all further statistical analyses. Kolmogorov–Smirnov normality tests revealed that the data violated this assumption and consequently non-parametric tests (Spearman’s rho) were used for all additional analyses.
There were no significant associations between age, years of education, verbal intelligence and depression, as evidenced by the WTAR, MADRS depression scores (see Table
Mean | SD | Min | Max | |
---|---|---|---|---|
Age | 34.05 | 13.66 | 18 | 64 |
Years of education | 16.27 | 2.83 | 9 | 27 |
WTAR scaled score | 112.30 | 8.11 | 83 | 129 |
MADRS | 1.79 | 3.01 | 0 | 26 |
The descriptive statistics for all neurocognitive variables are presented in Table
Missing |
Mean | SD | Range | TR | ||
---|---|---|---|---|---|---|
O-LIFE | ||||||
Unusual experiences | 171 | 2.3 | 4.98 | 4.86 | 0–25 | 0–30 |
Cognitive disorganization | 171 | 2.3 | 7.22 | 5.24 | 0–20 | 0–24 |
Introvertive anhedonia | 170 | 2.9 | 4.16 | 3.63 | 0–20 | 0–27 |
Impulsive non-conformity | 172 | 1.7 | 7.20 | 4.13 | 0–19 | 0–23 |
D-KEFS Inhibition V Color Naming | 168 | 4 | 10.54 | 8.21 | −5 to 37 | – |
D-KEFS Inhibition/Switching V Inhibition | 170 | 2.9 | 5.88 | 7.47 | −12.4 to 28.20 | – |
D-KEFS Inhibition/Switching V Color Naming | 170 | 2.9 | 12.81 | 11.60 | −4 to 49.6 | – |
D-KEFS Inhibition/Switching V Word Reading | 170 | 2.9 | 14.89 | 14.69 | −4 to 57 | – |
Trail Making Test – Part A | 173 | 1.1 | 25.56 | 8.91 | 11–68 | 300 s |
Mazes | 172 | 1.7 | 10.61 | 5.65 | 3–26 | 0–26 |
Letter–number sequencing | 173 | 1.1 | 16.79 | 2.59 | 10–24 | 0–24 |
Spatial span backwards | 175 | 0 | 8.95 | 1.80 | 2–14 | 0–16 |
To further explore relationships between schizotypy factors and neurocognitive variables, a two-tailed Spearman’s rho correlation analysis was conducted and results are presented below.
In terms of assessing inhibition, the analysis revealed a significant positive association between unusual experiences and inhibition versus color naming raw time [
The Spearman’s rho analysis also revealed a significant positive relationship between cognitive disorganization and inhibition versus color naming raw time [
Additionally, the exploratory analysis showed a significant positive association between impulsive non-conformity and inhibition versus color naming raw time [
In regards to attention and processing speed, the Spearman’s rho analysis showed a significant positive relationship between introvertive anhedonia and Trail Making Test – Part A [
In respect to planning and organization, a significant negative relationship between introvertive anhedonia and mazes raw score [
In relation to working memory measures, the analysis revealed a non-significant positive trend between unusual experiences and letter–number sequencing raw score [
The current study aimed to explore associations between schizotypy factors and cognition in an adult community sample. The key findings from this study were significant positive associations between unusual experiences, cognitive disorganization, and impulsive non-conformity and inhibitory latency and cognitive flexibility on the Color–Word Interference Test, once baseline color naming and word reading were controlled. Additionally, findings revealed a significant positive association between introvertive anhedonia and attention and processing speed on the Trail Making Test – Part A. Lastly, results showed a significant negative association between introvertive anhedonia and reasoning and problem solving on the mazes task and a significant positive relationship between impulsive non-conformity and reasoning and problem solving on the mazes task.
Our findings of associations between positive, cognitive, and asocial schizotypal traits and impairments in inhibition and cognitive flexibility or attentional switching (Color–Word Interference Test) are in line with past studies that have found high schizotypes to display greater inhibitory latency and less accurate responses compared with low schizotypes on all inhibition and switching conditions of the Color–Word Interference Test (
Furthermore, our results of a relationship between negative schizotypal traits and reduced attention and processing speed are consistent with past research reporting an association between negative and cognitive schizotypal traits and poorer sustained attention, as measured by the Continuous Performance Task, in a community sample (
Additionally, the current study found a significant negative association between introvertive anhedonia and completion time on a mazes task, suggesting that higher levels of negative schizotypy are related to poorer reasoning and problem-solving performance. This is consistent with previous schizophrenia research that found patients to demonstrate significant impairment on a mazes task in comparison with controls (
A couple of noteworthy methodological shortcomings exist in the current study. For instance, schizotypy factor scores identified in this study were below current normative scores for the O-LIFE inventory (
In addition, previous literature has suggested the use of illicit drugs to impact both schizotypy scores and cognitive performance, particularly inhibition (
In conclusion, the current study was one of the first in schizotypy literature to tease apart the relationships between factor scores and cognition in an adult community sample that accounted for psychiatric illness and family history. This allowed for the exploration of both cognitive functioning and potential compensatory mechanisms in individuals who have passed the peak onset times for developing schizophrenia. Findings from the current study further extend a limited body of schizotypy literature that enables inferences to be drawn in relation to the cognitive deficits seen in schizophrenia, without the potential confounds of illness chronicity and treatment medications. A better understanding of cognitive performance in schizophrenia is essential due to the vast experience of cognitive deficits and resistance to current treatment medications. Consequently, this research has potential practical implications for aiding in the establishment of treatments, to be used in conjunction with antipsychotic medication, for the cognitive symptoms of schizophrenia.
The authors report no commercial or financial for the current research. Caroline Gurvich was funded by a National Health and Medical Research Council (NHMRC) early career fellowship.
The Supplementary Material for this article can be found online at
The authors would like to thank the members of the Genes and Cognition Lab at the Monash Alfred Psychiatry Research Centre (MAPrc) for providing assistance and support with the current project. The authors would also like to thank MAPrc and the wonderful staff and students there. Lastly, the authors would also like to express their appreciation for all the participants who were involved in the research project for their time and patience. This research was funded in part by an NHMRC project grant APP1060664 awarded to SR, a Barbara Dicker Brain Science Foundation grant awarded to SR, CG and EN, CG was also supported by an NHMRC ECR fellowship and TVR was funded by Helen McPherson Smith, Australian Rotary Health/Bipolar Expedition and Swinburne University.