The impact of atypical antipsychotic medications on long-term memory dysfunction in schizophrenia spectrum disorder: a quantitative review

Abstract

This meta-analytic review examines the ef.cacy of antipsychotic medications in ameliorating schizophrenia-related long-term memory (LTM) impairments. Twenty-three studies were reviewed that compared schizophrenia spectrum patients treated (a) with atypical versus typical antipsychotic medications, or (b) with various atypical treatments. In 17 atypical versus typical trials aggregating 939 participants, superior overall (verbal and nonverbal) LTM was detected in patients assigned to atypical trials. However, this difference was small (effect size estimate (ES) 0.17; 95% Con.dence Interval (CI) 0.04 to 0.31) and speci.c to certain atypical treatments. Relative to typical antipsychotic trials, LTM superiority was marginally signi.cant for risperidone trials (ES 0.20; 95% CI 0.03 to 0.44) and signi.cant for olanzapine trials (ES 0.29; 95% CI 0.08 to 0.49). In contrast, clozapine trials did not produce a LTM advantage over typical trials (ES 0.06; 95% CI 0.35 to 0.23). Due to the lack of available studies, the effect of quetiapine was indeterminate. Direct comparison between atypical trials revealed a similar effect pattern. A marginally signi.cant superiority in overall LTM was detected for risperidone and olanzapine compared to clozapine (ES 0.28; 95% CI 0.04 to 0.59), which reached signi.cance for verbal LTM (ES 0.36; 95% CI 0.04 to 0.67). Finally, the bene.cial impact of antipsychotic medications emerged as a function of differences in the anticholinergic properties of the treatment arms being compared.