M123. EPISODIC VERBAL MEMORY DEFICIT IN SCHIZOPHRENIA: A MARKER OF PROGRESSION OF DISEASE OR DIFFERENT NEURODEVELOPMENTAL PATHWAYS FROM THE ONSET?

BACKGROUND: Episodic verbal memory primarily indicates acquisition or registration of memory for verbally presented information, being one of the main neuropsychological impaired functions in individuals with schizophrenia. Furthermore, it appears to be more susceptible than other memory systems to early neuronal dysfunction, supporting hypotheses about a neuroprogressive course of schizophrenia (SZ). On the other hand, it is unclear if such memory dysfunction in schizophrenia could not only be associated with illness progression, but also with neurodevelopment markers such as premorbid crystallized intellectual functioning (IQ). Therefore, we aimed to better understand the relationship between years of illness (YOI), IQ and episodic verbal memory in individuals with SZ. METHODS: We included 218 individuals with confirmed diagnosis of SZ from 3 separate centers (Hospital de Clínicas de Porto Alegre, Brazil; Hospital de Clínicas da Universidade Federal do Paraná, Brazil, and Hospital Clínic de Barcelona, Spain). All participants were informed about study procedures and signed consent before assessment. Participants underwent cognitive assessment with Hopkins Verbal Learning Test (HVLT) for episodic memory and Wechsler Abbreviated Scale of Intelligence for estimated crystallized premorbid IQ. We conducted a mediational analysis to estimate the effect sizes of years of illness in predicting memory deficits considering the indirect effect of IQ as a mediator, as well as age and sex as covariates. RESULTS: There was a significant indirect effect of years of illness on HVLT immediate recall through IQ, ab=-.119 CI 95% [-.248, -.013]. The mediator could account for more than a third of the total effect, PM=.39. The direct effect of years of illness on immediate recall was only a trend (c: -.09, p= .068), while the total effect counting IQ was significant (c’=-.15, p=.007). DISCUSSION: The effect sizes of IQ were greater than the direct effect of years of illness on memory deficits in our sample. This finding implicates that neurodevelopment markers such as IQ may be as important as disease progression itself in predicting cognitive outcomes in SZ. While patients with lower premorbid IQ appears to be more prone to memory deficits, those with better early intellectual development appears to count on a protective effect. Neuroprogression in schizophrenia would be an addition of neurodevelopment and disease progression. These results help to give new lights on the heterogeneity in the course of schizophrenia, different trajectories and the need of more personalized approach. Further prospective studies are mandatory.