Exploring the relation of depression and overt behavior with daily diaries.

Behavioral models of depression highlight decreased response-contingent positive reinforcement as critical toward conceptualizing depressive affect, decreased reinforcement being caused by changes in the quantitative (i.e., number or intensity) or qualitative (i.e., type or function) aspects of reinforcing events, availability of reinforcement, inadequate instrumental behaviors, and/or an increased frequency of punishment [Lewinsohn, P. M. (1974). A behavioral approach to depression. In R. M. Friedman, & M. M. Katz (Eds.), The psychology of depression: Contemporary theory and research. New York: Wiley]. Building on previous research and addressing methodological limitations, this study utilized a daily diary method and behavioral coding system to directly assess whether qualitative aspects (or types) of human behavior differed as a function of depression level. Relative to non-depressed individuals, mildly depressed participants engaged less frequently in social, physical, and educational behaviors and more frequently in employment-related activities. These data support behavioral models of depression and have clinical relevance as highlighted with reference to behavioral activation interventions for depression.