Sampling and recruitment
The overall sampling frame in the current study included 176 adolescents who were followed up at 12 months as part of the host trial (95 from the intervention arm; 81 from the control arm). We considered the principle of “information power” (i.e. the more information power the sample provides, the smaller the sample size needs to be; Malterud et al., The final qualitative sample consisted of 32 participants. This included 21 adolescents who received the counsellor‐led format in the original host trial, most of whom (