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.
Cognitive impairment has been consistently associated with severe psychiatric disorders like schizophrenia (SZ) and bipolar disorder (BD) (Vöhringer et al., 2013). SZ and BD present a similar cognitive deficits profile, although their degrees of dysfunction may be different (Vöhringer et al., 2013 and Schretlen et al., 2013). Multiple factors such as psychotic symptoms, recurrences, chronicity, drug abuse and medication may contribute to cognitive deficits in both disorders (Au et al., 2013 and the NAPLS group, 2014). Memory impairment is one of the core features of cognitive and functional decline in psychiatric population (Kuswanto et al., 2013, Schaefer et al., 2013 and Yatham et al., 2010).
Episodic memory (EM), an independent declarative memory system, is responsible for storage and conscious recall of past personal experiences that contains details about spatial and temporal context of these occurrences – what/when/where happened (Tulving, 2002). There is an interrelation with memory and other important cognitive domains, such as executive components and language. EM is highly sensitive to aging and to neurodegenerative diseases, and its performance is thought to be predictive of long-term outcome (Pause et al., 2013). Furthermore, in either BD or SZ, EM has been correlated with functioning in everyday life domains (Danion et al., 2007), especially in work performance (Tse et al., 2013 and Gilbert and Marwaha, 2013).
A novel approach to understand severe mental disorders is to adopt a clinical staging model (Wood et al., 2011). This model is useful as it differentiates early, milder clinical phenomena from those that accompany illness progression and chronicity (McGorry et al., 2010). Staging models for SZ (Agius et al., 2010 and Wood et al., 2011) and BD (Vieta et al., 2011, Kapczinski et al., 2009a, Kapczinski et al., 2009b and Berk et al., 2007) have been proposed in order to personalize and optimize treatments (Berk et al., 2009).
Although cognitive functioning is widely studied in SZ and BD, the performance of EM along the course and progression of both diseases has not yet been studied. Therefore, our goal is to ascertain whether SZ and BD show different patterns of episodic memory performance, according to their clinical stages.
