An experimental paradigm for triggering a depressive syndrome

Research investigating whether depression is an adaptation or a disorder has been hindered by the lack of an experimental paradigm that can test causal relationships. Moreover, studies attempting to induce the syndrome often fail to capture the suite of feelings, thoughts, and behaviours that characterize depression. An experimental paradigm for triggering depressive symptoms can improve our etiological understanding of the syndrome. The present study attempts to induce core symptoms of depression, particularly those related to rumination, in a healthy, non-clinical sample through a controlled social experiment. These symptoms are sad or depressed mood, anhedonia, feelings of worthlessness or guilt, and difficulty concentrating. 134 undergraduate students were randomly assigned to either an Exclusion (EX) or Inclusion (IN) group. Participants in the Exclusion group were exposed to a modified Cyberball paradigm, designed to make them feel socially excluded, followed by a dual-interference task to assess whether their exclusion interfered with their working memory. Excluded participants: (1) self-reported a significant increase in sadness and decrease in happiness, but not anxiety or calmness; (2) scored significantly higher in four of five variables related to depressive rumination; and (3) performed significantly worse on a dual-interference task, suggesting an impaired ability to concentrate.

Methods
Our datasets were collected through LimeSurvey, an open source on-line statistical survey web app. We first exported our data as excel files which contain participants' self-reported data. We also added the scores for each participants' writing task provided by our blind-raters. We have presented the data from our primary study and our pilot study in two seperate files.