Overall levels of depression were low, but they varied as a function of participant group and phase. Specifically, while the Prisoners were more depressed than the Guards at the start of the study, by its end, this situation had reversed.
This pattern was confirmed by analysis which revealed a significant statistical interaction between participant group and phase. Further analysis showed that the Prisoners’ depression decreased significantly over time. The Guards’ depression increased over the course of the study, but not significantly.
- Source: Reicher, S. D., & Haslam, S. A. (2006). Rethinking the psychology of tyranny: The BBC Prison Study. British Journal of Social Psychology, 45, 1-40.