Cognitive vulnerability differentially predicts symptom dimensions of depression.

Background: We examined the association of cognitive vulnerability to depression with changes in homogeneous measures of depressive symptoms.

Methods: Baseline and 1-year follow-up data were obtained from 2981 participants of the Netherlands study of depression and anxiety. Multivariate regression analyses were carried out on cognitive reactivity, locus of control and implicit and explicit self-depressive associations in combination with negative life events. The purpose of this analysis was to predict changes on the mood/cognition and anxiety/arousal subscales of the inventory of depressive symptomatology - self report.

Results: Cognitive reactivity, locus of control and explicit self-depressive associations were independently associated with changes in depressive symptoms after adjustment for covariates and baseline severity (all p<0.01). Negative life-events interacted with cognitive vulnerability to depression to predict depressive symptoms. Locus of control (b1=0.16, SE=0.02, η(2)=0.01; b2=0.10, SE=0.02, η(2)=0.004, F=8.69, p<0.01) and explicit self-depressive associations (b1=0.10, SE=0.03, η(2)=0.02; b2=0.02, SE=0.04, F=7.50, p<0.01) were more strongly associated with the cognitive (b1) than the somatic (b2) symptom dimension of depression.

Limitations: The study sample is over-inclusive of depressed patients. Therefore it might be problematic generalizing the findings to the general population.

Conclusion: Cognitive etiological factors may play a role in a "cognitive" subtype of depression. The findings strengthen the notion that homogeneous measures of depressive symptoms enable a greater degree of discrimination between subtypes than a multidimensional conception of depression.