Background. Non-attendance at colonoscopy is associated with reduced colorectal cancer (CRC) survival.

Purpose. The aim of this research was to quantify barriers to colonoscopy and test the effectiveness of behaviour change techniques (BCTs) to address them.

Methods. Two studies were performed. In the first study, participants were asked to imagine their next CRC screening result was abnormal and were presented with the standard abnormal result letter used in the English CRC Screening Programme. Participants then completed a short survey. Multivariate regression tested associations between perceived barriers and intentions. In the second study, participants were randomly presented with a modified version of the abnormal results letter, which incorporated one or more BCTs, designed to target barriers identified in Study 1, using a 2⁸ factorial design. Participants then completed the same survey used in Study 1. Multivariate regression tested the effectiveness of the BCTs to modify target barriers and intentions.

Results. In Study 1, five items were associated with intentions, namely: ‘Lack of understanding that CRC can be asymptomatic’, ‘Perceived importance of screening’, ‘Transport/travel’, ‘Shared decision making and family influenced participation’ and ‘Fear of pain and discomfort’ (all p’s<0.05). In Study 2, the inclusion of a social support message, targeting ‘shared decision-making and family influenced participation’, facilitated independent decision making and increased intentions (both p’s<0.05). There was no evidence to support the remaining seven BCTs to modify barriers or intentions (all p’s <0.05).

Conclusions. Inclusion of a social support message facilitated independent decision making and improved intentions.