Intrusion errors in explicit memory: Their differential relationship with clinical and social outcome in chronic schizophrenia

Abstract

Introduction. Memory deficits might account for clinical and adaptive differences between groups of patients with chronic schizophrenia. We investigated the qualitative factors of memory that influence clinical and social status.

Methods. Psychosocial functioning, clinical symptoms, and memory function were assessed in 99 patients at four time points over a 16-month period using recall scores for semantically related words, unrelated words, paired associated learning, and word span. An initial cluster analysis using symptom assessment data from all four time points divided the sample into three groups: patients with low symptoms ratings that remained stable throughout the study period (low symptom-stable group—LSSG; N=51); patients with initially high symptoms ratings that subsequently improved (high symptom-improved group—HSIG; N=32); and patients with initially high symptoms ratings that deteriorated during the follow-up (high symptom-deteriorated group—HSDG; N=16).

Results. Memory was better preserved in LSSG compared to HSIG and HSDG patients. Recall performance was generally better for semantically related words than for unrelated words but the difference between LSSG and the two other groups was more constant over time for semantically related words. Extra-list errors variable was positively correlated with three PANSS measures (r=.25−.47). Also, the extra-list errors scores were correlated with the Magical Ideation Scale (r=.34–.39). Memory scores (global explicit, unrelated, related) were significantly and positively correlated with independent living skills (r=.26–.55) and the extra-list errors were negatively correlated with both social support and independent living skills (r=−.29 and r=−.46, respectively). All groups showed a reduction in extraneous false recognition errors/intrusions (FRIs) over time with the HSIG showing the greater change. HSIG and HSDG patients committed slightly more FRIs in recall tasks (extraneous information) than LSSG patients.

Conclusion. Memory performance is better in patients presenting with less severe symptomatology. The extent to which FRIs reduce over time in patients with schizophrenia is a novel finding.

This research was funded by Fonds de la Recherche en Santé du Quebec (FRSQ). We thank Martin Lepage, Todd Woodward, and Adham Mancini-Marïe for their useful comments and suggestions on this article.