Objective: Regular screening for colorectal cancer (CRC) can substantially improve outcomes. This study investigated how measuring regret expected from failing to screen might lead to stronger screening intentions. Five potential moderators were evaluated: perceived threat, psychological reactance, prior screening participation, concurrently measuring faecal aversion (FA) and anticipated regret (AR). Design: A 2 (AR measured pre/post intention) × 2 (FA measured pre/post intention) single blind parallel randomised controlled trial was used. Australians aged 45 and over completed an online survey measuring AR, FA, intention, theory of planned behaviour variables and potential moderators. Main outcome measures: The primary outcome was CRC screening intention. Results: Eight hundred and three participants were randomised, with 666 analysed. Measuring AR prior to intention unexpectedly resulted in a significantly lower intention to screen (d = 0.18, 95% CI [0.03, 0.33]) compared to measuring after intention. Trait reactance predicted a significantly lower intention when it was at least 0.52 SD above the mean; other moderators were not supported. Conclusion: The processes underlying anticipated regret manipulations must be better understood in order to have practical value in health promotion. More research is required to determine how to minimise or avoid the apparent negative effects of psychological reactance in CRC screening communication. Trial registration: Australian New Zealand Clinical Trials Registry: ACTRN12618001098224 http://www.ANZCTR.org.au/ACTRN12618001098224.aspx.
Keywords: Australia; Colorectal neoplasms; emotions; health behaviour; health promotion; intention.