Meta-analysis of the changes in correlations between depression instruments used in longitudinal studies

Abstract Background Correlations between instruments measuring the same construct reflect their concurrent validity. Little is known about changes in correlations between such instruments employed in studies with repeated assessment. The aim of this meta-analysis was to examine the changes in correlations between depression instruments in the course of longitudinal studies. Methods A literature search was conducted using MEDLINE and PsycINFO for the period from 1960 to 2013. The total number of collected articles was 3723, of which 61 were included. Three meta-analyses were performed for the changes in correlations between each pair of the three depression scales: Hamilton Rating Scale for Depression (HAMD), Montgomery–Asberg Depression Rating Scale (MADRS) and Beck Depression Inventory (BDI). The effect size in these meta-analyses was obtained by the z-transformation of correlation coefficients. Results Correlations between depression scales increased over time in 52 studies. Significant changes in correlation coefficients were found for correlations between HAMD and BDI ( p