Content overlap inflates the relation between negative cognition and dysphoria

We investigated whether the presence of items assessing negative cognition on the Beck Depression Inventory (BDI) inflates the relation between BDI scores and measures of negative cognition. In four student samples, we examined the relation between measures of self-esteem, dysfunctional attitudes, control beliefs, perceived social support, and BDI scores calculated with and without negative cognition items. There were significant reductions in the strength of the relations between self-esteem, dysfunctional attitudes, and BDI scores when overlapping content was removed. Moreover, this was not due to the increase in error variance resulting from reducing the number of items on the BDI. Although the magnitude decreased, the relation between negative cognition and dysphoria remained significant in all comparisons even when overlapping content was removed. Thus, although content overlap appears to inflate the relation between some measures of negative cognition and dysphoria, it cannot completely account for their relation.