Covariation bias in depression - a predictor of treatment response?

Covariation bias, defined as an overestimation of the relationship between fear-relevant stimuli and aversive consequences, is a well-investigated cognitive bias in anxiety disorders. As patients with affective disorders also show biased information processing, the aim of the present study was to investigate whether depressed patients also display a covariation bias between negative stimuli and aversive consequences. Covariation estimates of 62 inpatients with a current severe depressive episode were assessed at admission (n = 31) or after 6 weeks of treatment (n = 31) and were compared in a between-group design with 31 age- and sex-matched healthy controls. All participants showed a covariation bias for the relationship between negative stimuli and aversive consequences. Moreover, covariation bias at admission was significantly associated with various clinician- and self-reported dimensional measures of treatment response assessed 6 weeks later (Global Assessment of Functioning, Clinical Global Impression Scale, and Beck Depression Inventory), i.e., patients with a stronger bias showed greater impairment after 6 weeks of treatment. Categorical analyses revealed that overall, treatment non-responders-but not responders-were characterized by a covariation bias. The naturalistic study design without standardized pharmacological and psychotherapeutic treatments is a central limitation. We conclude that the covariation bias may constitute a possible marker in the field of emotional information processing in the search for effective predictors of therapy outcome.