Toward a meta-analytic approach of sex differences in episodic memory of schizophrenia patients: Exploratory findings

Studies in the general population have demonstrated the existence of sex differences in cognitive function. In terms of memory, women outperform men on verbal, whereas men exhibit either superior or comparable nonverbal episodic memory. The results obtained in schizophrenia patients have been more variable. The main objective of the present study was to combine available data and perform preliminary analysis of potential differences between men and women with schizophrenia on verbal and nonverbal episodic memory. Systematic electronic literature searches via PubMed, PsychINFO, MEDLINE In-Process and other non-indexed citations, and EMBASE yielded seventy-four articles out of which ten matched our prespecified inclusion and exclusion criteria. The analysis revealed that sex differences in schizophrenia in nonverbal memory function were consistent with that which has been observed in the general population (men outperforming women). In contrast, the nonsignificant effect in verbal memory suggested a loss of normal sexual dimorphism (women outperforming men), possibly due to the differential effect that schizophrenic illness exerts on neurocognitive function in men and women. These preliminary results imply differential effects of schizophrenic illness on men and women, and call for considering sex differences in clinical cognitive trials with medications.