Verbal episodic memory along the course of schizophrenia and bipolar disorder: a new perspective

Impairment on episodic memory (EM) has been strongly correlated with psychiatric disorders, including schizophrenia (SZ) and bipolar disorder (BD). Morevover, the effects of course and progression of the illness on cognitive functioning have not been well established. The aim of the present study is to assess performance of episodic memory in BD and SZ according to their clinical stages. Subjects who met DSM-IV criteria for bipolar disorder (n=43) and schizophrenia (31), on euthymia or clinical remission, were recruited from the outpatients facilities at Hospital de Clínicas de Porto Alegre (Brazil). They were classified into two clinical stages (early or late for BD, and recent onset or chronic for SZ) and compared to 54 healthy controls. Episodic memory performance was assessed by means the Hopkins Verbal Learning Test-Revised (HVLT-R) that measures verbal learning and episodic memory in both disorders. Our results showed that patients in early stage of BD (EBD) performed better performance on the total immediate free recall (p<0.0001, F=12.060) as well as in delayed free recall (p<0.0001, F=13.914) compared to late stage (LBD) and SZ groups. In the ability to retain words learned, LBD and chronic (CSZ) were more impaired than other groups. Furthermore, the variation of learning (i.e, learning effects) along the 3 trials of immediate free recall was similar between groups. In conclusion, we found a cognitive decline alongside with the progression of BD whereas such impairment was evident in the early of SZ. Despite this, both groups (BD and SZ) seem to maintain the ability to learn. It emphasizes the relevance of studying new therapeutic strategies, in particular, cognitive rehabilitation/remediation techniques as promissory treatment for psychiatric patients, even in those with moderate disabilities.