La conscience des déficits neurocognitifs dans la schizophrénie : une méta-analyse

Abstract

Background Schizophrenia is well-known to be associated with a lack of insight into symptoms. Comparatively, little is known on insight into neurocognitive deficits in schizophrenia, despite the fact that these dysfunctions are undoubtedly core features of the disorder. Recently, growing interest has been paid to subjective cognition, and thus far, results have been heterogeneous. The objectives of current meta-analysis were to determine the magnitude of subjective complaints in schizophrenia; to examine the association between subjective cognitive complaints and objective cognition, as well psychiatric symptoms and insight into illness. The meta-analysis also sought to determine if results are influenced by the choice of the scale used to measure subjective cognition. Methods A search was performed with PubMed, PsycInfo and EMBASE, using the following key words: schizophrenia OR psychosis AND cognition OR memory OR attention OR "executive functions" AND insight OR "subjective cognition" OR awareness. Studies involving patients with schizophrenia-spectrum disorders and measuring subjective cognition with a validated self-report scale were included. Studies using scales measuring insight into thinking processes (e.g. Beck Cognitive Insight Scale) were excluded. Statistical analyses were performed with the Comprehensive Meta-Analysis-2 software. Cognitive scores were grouped into 6 cognitive domains (as recommended by the MATRICS group): attention, problems solving, speed of processing, verbal memory, visual memory and working memory. The difference in cognitive complaints between schizophrenia patients and healthy controls was examined using Cohen's d. The associations between subjective cognition and objective cognition, psychiatric symptoms and insight into illness were examined using Pearson's correlation coefficients. Results Twenty-two studies were retrieved, including a total of 1609 patients and 294 controls. Patients reported increased subjective cognitive complaints, compared to controls (moderate effect size). A weak association was observed between subjective and objective (global) cognition. The association was larger in studies using the Subjective Scale To Investigate Cognition in Schizophrenia (SSTICS), compared to studies using other scales. The largest association was observed between subjective complaints and problem solving. The association between subjective complaints and depressive symptoms was in the same range as the association between subjective complaints (measured with the SSTICS) and objective cognition. No association was found between subjective complaints and positive / negative symptoms. Finally, a weak association was found between subjective complaints and insight into illness. Discussion Taken together, these results suggest that schizophrenia patients report significant subjective cognitive complaints. However, patients have a poor understanding of these deficits, since subjective complaints are as strongly associated with depressive symptoms as they are associated with objective cognitive deficits. Schizophrenia patients may be more aware of their problem solving deficits. However, this observation is based on a limited number of studies and will need to be replicated in future studies. Our results also show that insight into neurocognitive deficits is largely independent from insight into illness. Finally, the results of the current meta-analysis may have methodological implications, since they suggest that the SSTICS produces stronger associations between subjective and objective cognition than other scales. In the future, greater attention will need to be paid to the domains of subjective complaints, as well as to subjective cognitive complaints in other psychiatric disorders.