Attributions and depression: Why is the literature so inconsistent?

A large body of literature examining the relations between depression and causal attributions has produced inconsistent findings. Many studies have clearly had inadequate statistical power, however, so that negative findings cannot be readily interpreted. In this review, statistical power was computed for all published analyses relating depression to attributions to any of the following: internal, stable, or global causes, or their composite, ability/character, effort/behavior, luck, or task difficulty. On average, the power of these analyses was very poor. For example, only 8 of the 87 analyses had a probability of .80 or better of detecting a small-medium true population effect (e.g., r = .20). Separating studies by levels of power helped to clarify the inconsistencies in the literature. Whereas across all published studies depression was fairly consistently related only to the composite of internal, stable, and global attributions, those few studies with fairly high power all reported significant relations of depression to stable and global attributions as well as to the composite. It is suggested that increased attention be paid to the power of statistical analyses in planning studies and in drawing conclusions from completed studies.