Methods
Three hundred and ninety-three UK adults who had previously self-harmed were exposed to the same intervention at baseline and, six months later, were randomly allocated to receive either: (a) the same version of the intervention (control group), or (b) a version of the intervention that had been refined following participant feedback (experimental group). The main outcome measure was acceptability ratings for each of the seven domains specified in the Theoretical Framework of Acceptability (TFA).