A systematic review and meta-analysis of cognitive remediation in early schizophrenia
Introduction
The majority of the costs of schizophrenia ($63 billion in the USA in 2002, £12 billion in the UK in 2011) are not for treatment but are consequences of disability, e.g. indirect costs associated with care and loss of productivity (Andrews et al., 2012, Wu et al., 2005). The cognitive impairment evident in schizophrenia is a key driver of poor social functioning (Brekke et al., 2007, Brekke et al., 2009). Deficits are seen in all areas of cognitive functioning (Heinrichs and Zakzanis, 1998) but social cognitive deficits arguably most directly drive dysfunction (Bora et al., 2006, Brekke et al., 2005, Couture et al., 2006).
Longer duration of untreated psychosis has been linked to worse cognitive function (Scully et al., 1997), suggesting that intervention close to the onset of psychosis is required to reduce the cognitive deficit and its subsequent impact on quality of life. Early intervention is known to reduce positive and negative symptoms (Petersen et al., 2005), significantly reduces the risk of relapse and the number of hospital admissions (Bark et al., 2003) and has positive effects on social and occupational functioning (Craig et al., 2004, Marshall and Rathbone, 2011). The level of functioning during the first years following the onset of psychosis can predict long term outcome (Birchwood et al., 1997, Harrison et al., 2001). Given the effectiveness of early intervention in other domains of schizophrenia, employing cognitive remediation (CR) treatment early in the course of schizophrenia would be expected to lead to improve long-term functional outcome.
Whatever the cognitive benefits of current antipsychotics, their effectiveness in specifically improving cognition sufficiently to benefit social function is undemonstrated, and specific cognition enhancing medications are not yet clinically available. This makes CR an attractive interventional strategy. CR is defined as a behavioural training-based intervention that aims to improve cognitive processes such as attention, memory, executive function, social cognition and metacognition with the goal of durability and generalisation (Cognitive Remediation Experts Workshop, Florence, April 2010). Meta-analysis shows that CR is effective across a wide range of cognitive domains (Wykes et al., 2011), particularly for social cognition, reasoning and problem solving. CR programmes that include an element of strategy training and are linked to rehabilitation programmes are most effective for improving functioning outcomes.
Successful CR trials have been conducted in a range of settings but few have studied the effectiveness of the intervention in early schizophrenia. If the time of first presentation is a “critical period” for cognitive decline, as with other symptoms (Birchwood et al., 1998), it is particularly important to determine the efficacy of CR at this point. There is some evidence that patients who receive CR at a younger age (Wykes et al., 2009) and at an earlier stage of schizophrenia (Bowie et al., 2014, Gupta et al., 2011, Lee et al., 2013) have greater functional, social and cognitive gains than older populations with the illness. Although a recent review of CR in early schizophrenia has been undertaken (Barlati et al., 2012), there is not yet a systematic review and meta-analysis of CR trials in this early phase, and several such trials have been conducted since the last major review of the area (Wykes et al., 2011). We therefore set out to conduct such a specific review and meta-analysis.
In this study, we hypothesised that CR would have a positive effect on cognition, symptoms and functioning of those experiencing a first episode of psychosis. We also hypothesised that this effect would be moderated by participant and treatment characteristics.
Section snippets
Data sources
Databases were searched independently by two authors (ER and ZK) and included all abstracts published up to May 2015. The Cochrane Controlled Trials Register, PsycINFO, Embase, MEDLINE and Web of Science were searched using the terms:
(Cognit*) AND (remediation OR rehabilitation OR training) AND (early course OR early OR first episode OR adolescent) AND (schiz* OR psychosis OR psychotic).
Reference lists were hand-searched and first authors of included reports and those known to be conducting
Corpus of studies
Table 1 shows summary characteristics of the eleven unique primary studies included in the review. Funnel plots showed no evidence of publication bias.
Participants over all of the studies were young (mean age 21.8), the majority were male (63%) and they had low baseline symptoms (an average rating of 2.4 on an item (scale 1–7) in the PANSS or BPRS). Most participants were taking antipsychotic medication although eight studies included participants taking no medication (range 3–24%).
Discussion
This meta-analysis is the first to investigate the efficacy of CR in early schizophrenia. After sensitivity analysis to exclude studies with significant baseline differences between treatment conditions, CR at this stage had a positive effect on global cognition, especially on verbal learning and memory and social cognition. Improvements nearing uncorrected significance were also seen in processing speed, working memory and in reasoning and problem solving. This pattern mimics that seen in the
Contributors
ER and ZK collected the data; ER performed the analysis; ER wrote the first draft and all authors contributed to revision of the manuscript prior to submission.
Role of the funding source
No funding source played any role in this study.
Conflict of interest
JCN has received expenses to attend conferences and fees for lecturing and consultancy work (including attending advisory boards) from the manufacturers of various antipsychotic drugs. All other authors declare no conflict of interest in relation to this manuscript.
Acknowledgements
This work was supported solely by funding from the University of Manchester (AA10809).
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