Elsevier

Schizophrenia Research

Volume 182, April 2017, Pages 31-41
Schizophrenia Research

The course of cognitive functioning after first-episode of psychosis: A six month follow-up study

https://doi.org/10.1016/j.schres.2016.10.017Get rights and content

Abstract

Our aim with the present study was to evaluate rank-order and mean-level cognitive functioning stability among first-episode psychosis (FEP) patients, measured using the Cambridge Neuropsychological Test Automated Battery (CANTAB), over a six month period. We also aimed to examine longitudinal measurement invariance and identify factors—such as age, gender, educational level, treatment and psychopathological change scores—potentially linked to cognitive change among patients. In addition, correlations between objectively measured and subjectively evaluated cognitive functioning were estimated. Neuropsychological assessments were administered to 85 patients after the initial stabilisation of their psychosis; 82 of the patients were retested. Subjectively perceived cognitive functioning was measured using a subscale derived from the Estonian version of the Subjective Well-Being Under Neuroleptic Scale (SWN-K-E). On average, executive functioning and processing speed improved significantly, while memory test scores decreased significantly, over time. Very high rank-order stability (r = 0.80 to 0.94, p < 0.001) was observed with all measured ability scores. Confirmatory factor analysis revealed the loadings of a single (broad ability) factor model were equal across both measurement occasions, but the lack of intercept invariance suggested that mean-level comparisons are more appropriately carried out at a subtest level. On average psychopathology scores and antipsychotics doses declined over time, with the latter also significantly correlating with better executive functioning. Gender was a significant moderator of some domains of cognitive performance, and decline tended to be somewhat more pronounced for women. The results also indicated the lack of any relationship between objective and subjective measurements of cognitive functioning.

Introduction

Among other symptoms, psychotic illnesses are accompanied by neuropsychological impairments (Green et al., 2004, Kurtz, 2005). Although individual patient's neuropsychological profiles may be heterogeneous (Joyce et al., 2005), they are typically characterised by attention, set shifting, processing speed, memory, learning, working memory, and executive function deficits (Heinrichs and Zakzanis, 1998, Mesholam-Gately et al., 2009, Saykin et al., 1991), something that can be broadly summarised as generalised cognitive impairment (Dickinson et al., 2004, Mohamed et al., 1999). On average, schizophrenia patients tend to score 1.0 to 2.5 standard deviations lower in general cognitive ability compared to control subjects (CoS), however there is also some variability in the extent of impairment between domains (Bilder et al., 1992, Heinrichs and Zakzanis, 1998, Keefe, 2014, Mohamed et al., 1999). While some patients do fall within the normal range of ± 1 standard deviations of the mean of a generally healthy population (Kremen et al., 2000, Palmer et al., 1997). Hoff et al. (2005) concluded that although most FEP patients have undergone considerable cognitive decline by the time of their first hospitalisation, the exact course of cognitive impairment remains unknown. In addition, psychotic symptoms may even share some genetic aetiology with cognitive functioning (Kendler et al., 2015, McIntosh et al., 2013).

The available evidence is also contradictory as to whether cognitive functioning continues to decline during later stages of schizophrenia (Aas et al., 2014, Rund et al., 2007). It has been argued that the majority of such cognitive declines occurs just before or within a few years after the onset of psychosis (Bora and Murray, 2014). To date, longitudinal studies have investigated patients' cognitive functioning over the years following disease onset, but less is known about what specifically happens to their cognitive abilities during the months immediately following FEP diagnosis. Investigating the cognitive performance of patients during the early stages of chronic psychotic disorder may help to identify cognitive deficits related to schizophrenia, compared to cognitive dysfunction resulting from the long-term course of the schizophrenic illness or the treatment of either.

During the present study we investigated cognitive changes among FEP patients following their FEP. First, mean-level changes were calculated to ascertain the extent to which patients' cognitive abilities had changed during the six months following FEP. Second, the extent to which patients retained their cognitive test score ranking (rank-order stability) was examined. The lower the stability, the more likely there are potentially identifiable factors that result in deviation from the normative change pattern of a condition (Deary, 2014). Third, the structure of changes were examined, indicating the extent to which changes happened in lockstep, and therefore were likely to pertain to cognitive functioning in general, as opposed to specific cognitive domains. Fourth, individual differences in cognitive changes were compared to possible causal factors, including demographic characteristics, antipsychotic medication dosages, and the extent of psychopathology. In addition to cognitive functioning quantified using objective performance tests, subjective cognitive dysfunction may be an important early indicator of schizophrenia, as it can precede prodromal symptoms (Hambrecht et al., 2002, Nuechterlein and Dawson, 1984) is prevalent among patients with FEP (Moritz et al., 2000) and in the late stages of the disorder (Homayoun et al., 2011, Stip et al., 2003). During the present study, changes in subjective cognitive dysfunction were also recorded over the same timeframe. As it is currently unclear to what extent subjective and objective cognitive dysfunction measurements are in-line each other—some studies report positive correlations (Prouteau, 2004, Stip et al., 2003) and others no significant correlations (Homayoun et al., 2011, Zanello and Huguelet, 2001)—we correlated levels of change between measurements of objective and subjective cognitive dysfunction.

Section snippets

Study participants

The FEP patients were part of an on-going longitudinal research project of first-episode psychosis conducted by the Psychiatry Clinic of Tartu University Hospital, Estonia. A total of 85 patients (mean age 26.99 years old, s.d. = 6.96, range 18–43; 54.12% male; 92.94% right-handed) met the inclusion criteria: aged between 18 and 45; had experienced FEP; the duration of untreated psychosis was less than three years; they had received no antipsychotic treatment before their first contact with

Patients characteristics

Females were older (27.49 years old, s.d. = 7.05) than males (26.57 years old, s.d. = 6.94) and had undergone more formal education (mean for females: 13.51 years, s.d. = 2.16; mean for males: 12.64 years, s.d. = 2.72), although these differences were not statistically significant (t =  0.61, p = 0.55; t =  1.61, p = 0.11, respectively). Mean general psychopathology score, measured using BPRS, was 24.18 (s.d. = 12.80) at baseline and 19.31 (s.d. = 11.37) at follow-up (t =  4.24, p < 0.0001). Total BPRS CSs was

Discussion

The main aim with this study was to analyse whether and how cognitive functionality changes among 82 psychiatric patients directly after confirmation of an FEP diagnosis. In these data, mean-level changes (deviations from individuals' predicted scores based on performances at the first testing occasion) occurred in episodic memory, processing speed, mental flexibility, and executive functioning; patients tended to maintain their cognitive performance relative to other patients; there was

Conflict of interest statement

The authors declare no conflict of interest.

Contributors

Liina Haring designed the study, wrote the first draft of the manuscript. René Mõttus conducted data analysis, edited the manuscript and provided guidance throughout writing. Liina Haring and Kärolin Kajalaid participated in collection of cognitive assessment data. Kärt Uppin and Kadri Koch contributed to subject recruitment and clinical assessment. Eduard Maron and Eero Vasar supervised this project. All authors have critically reviewed the manuscript for important intellectual content, and

Role of the funding source

This research was supported by the grants from the Estonian Research Foundation (IUT 20-41, IUT 20-45) and the European Union through the European Regional Development Fund (Project No. 2014-2020.4.01.15-0012).

Acknowledgments

The authors are grateful to patients and control subjects for their participation in the study, and the colleagues who facilitated our work.

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      Thus, these results suggest that cognitive impairment is relatively stable after a FEP, but when patients do show changes they are more likely to improve than to decline. In fact, longitudinal studies in first episode patients have shown that most of the functions affected seem to improve modestly after the start of treatment (Hill et al., 2004; Haring et al., 2017). Our study suggests that in SSD patients, those subjects with a lower SES, early age of onset, higher negative symptoms, lower CR and worse cognitive performance have an increased risk of cognitive impairment at follow-up, which is in accordance with previous publications in which a large correlation between CR, SES, negative symptoms and cognition have also been reported (Puig et al., 2017; Amoretti et al., 2018).

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