Background: This study tested whether asking people to rate their anticipated feeling regret (AR) for not registering as a posthumous organ donor increases subsequent verified organ donor registration. Method: 14,509 members of the UK general public were randomly allocated to 1 of 4 arms. Participants in the no-questionnaire control (NQC) arm were asked if they were registered as an organ donor. Participants in the questionnaire control (QC) arm answered the same questions plus questions regarding their affective attitudes towards donation and their intention to register as an organ donor. Those in the TPB arm received the same items as the QC arm, plus items measuring their attitudes towards organ donation, subjective norm and perceived control. Those in the AR arm received the same items as the TPB arm, plus two items measuring AR for not registering as an organ donor. 6 months later, the UK transplant register was searched. Findings: People in the NQC condition were more likely to register as an organ donor (6.39%) than participants in the QC (5.27%), TPB (5.40%), and AR (4.51%) arms. Discussion: A brief AR intervention did not lead to an increase on organ donor registration.
