Cognitive and biochemical processes in depressed adult outpatients: a test of the circular process model.

The circular process model is a psychobiological model of depression, in which it is postulated that catecholamines and negative cognitions interact to influence depression. Since its publication, there have been no empirical tests to support or refute the model. This study tested the model in 92 depressed adult outpatients with non-bipolar non-psychotic depression. There were no significant bivariate correlations among the biochemical and cognitive measures. However, the interactive model was supported by results of two out of three hierarchical regression analyses, in which the biochemical-by-cognitive interactive terms significantly predicted depression after the main effects of each variable were accounted for. These findings show sufficient evidence in support of the Circular Process Model to warrant further testing over the treatment period.