Depressive Response Sets due to gender and culture-based Differential Item Functioning

Two studies tested a “strong” version of Nolen-Hoeksemaʹs [Nolen-Hoeksema, S. (1987). Sex difference in unipolar depression: evidence and theory. Psychological Bulletin, 101, 259–282.] hypothesis of depressive response sets using samples of Australian respondents (Study I, n=1111) as well as US respondents (Study II, n=300), using a Rasch version of Thalbourneʹs Manic-Depressiveness Scale (MDS) whose contents are consistent with atypical depression (i.e. depressive episodes with hypomanic symptoms). As predicted, tests for differential item functioning in both studies revealed that women are more likely to worry about “being poor” than equally depressive men (P<0.05), thus ruling out the alternative hypothesis that depressive response sets are simply a byproduct of more frequent or stronger depression in women. Australian women and men, and US women used the MDS items in a similar fashion, whereas equally depressed US men seriously underreported their symptoms. Yet, using top-down purification to derive an unbiased baseline set of items, a “split” 12-item Rasch measure (R-MDS) could be developed that is not affected by differential test functioning due to gender or cultural differences. Comparison of the R-MDS measure and the original MDS scores revealed that while women are more depressive than men by 0.4 SD, the absence of gender bias in the R-MDS decreased this effect by about 20% (0.08 SD). Moreover, gender bias interacted with culture, suggesting that comparisons of depression levels of diverse groups within the same culture may be biased as well. Raw score to R-MDS conversion tables are included.