Depression and cognition:: New insights from the Lorenz curve and the Gini index

This ex post facto prospective study reports the use of statistical techniques known as the Lorenz curve and Gini index to analyze the content of depressive cognitions as a function of attributional negative style (i.e., internal, global and stable causal attributions for failure or negative events, as proposed by the learned helplessness model) and negative cognitive triad (i.e., a negative view of oneself, ones future and ones world, according to Beck's cognitive model of depression). These statistical techniques revealed that attributional style was poorly related with depression level, whereas the negative cognitive triad showed a close relationship and provided a more accurate description of the depressive cognitive pattern. We also document how the Lorenz curve and Gini index can be used to assess the predictive capacity of different instruments or the strength of the relationship between different variables and psychological disorders, and to evaluate different models proposed to explain these disorders. This pioneering study reveals the potential usefulness in Psychology of these statistical techniques, mainly used in Economical sciences, for analyzing the validity of different factors and possible predictors of specific psychological disorders, or to enhance existing instruments, as our present study with depression shows.