Schizophrenia Bulletin, 2017, Vol. 43(suppl1), pp.S129-S129
Background: There are significant deficits in verbal learning in patients with schizophrenia, and this cognitive process is dependent on a network of regions including the hippocampus. The hippocampus is thought to play a key role in the development of psychosis and is reduced in volume in patients with schizophrenia. The purpose of this meta-analysis is to examine whether the deficits in verbal learning observed in schizophrenic patients are related to hippocampal volume reduction. Methods: The PubMed database was searched for studies reporting both verbal memory scores and hippocampal volume in patients with schizophrenia or those with a genetic high risk (GHR) until June 2016, and the reference lists of eligible articles were searched for further relevant articles. Seventeen studies met the inclusion criteria and comprised 755 schizophrenic patients (SCZ), 232 genetic high risk (GHR), and 914 healthy controls (HC). A restricted maximum likelihood random effects model was used to calculate the pooled correlation coefficient between hemisphere (left, right, or total) and type of recall (immediate or delayed) for each diagnostic group individually (SCZ, GHR, and HC). This was done using MetaNSUE, a meta-analytical method that allows the inclusion of statistically nonsignificant unreported correlation coefficients. Results: In patients with schizophrenia, left hippocampal volume positively correlated with immediate ( r = 0.26, 95% confidence interval [CI], 0.09–0.41) and delayed ( r = 0.13, 95% CI, 0.04–0.22) verbal recall. The same was found in the right hemisphere, (immediate: r = 0.23, 95% CI, 0.09–0.36; delayed: r = 0.23, 95% CI, 0.13–0.33). There was also a correlation between total hippocampal volume and delayed recall ( r = 0.23, 95% CI, 0.04–0.41). None of these correlations were significant in healthy controls. There was a positive correlation between left hippocampal volume and immediate recall only, in the GHR group ( r = 0.36, 95% CI, 0.15–0.53). Conclusion: The results from this meta-analysis suggest that hippocampal volume affects immediate and delayed verbal learning capacity in schizophrenia. This provides further evidence of hippocampal dysfunction in the pathophysiology of schizophrenia which may be an important therapeutic target in the future.
Oxford University Press