Table 6 The main themes and subthemes and illustrative quotations from the barriers-to-participation interviews with 5 patients who declined to take part and 5 informal caregivers

Medication concerns

A risking to stability: ‘It takes a long time to get stable, I didn’t want to mess with that’ (patient 3).

Previous switching experience: ‘I felt terrible for 6 months’ (patient 1); ‘It was quite hard, I was quite poorly’ (patient-participant 3); ‘I didn’t want to start having side effects again’ (patient 4).

Irreparable deterioration: ‘these [tablets] allow us to live our lives. You don’t to start messing with that in case you can’t get it back (patient 4).

Accessibility of materials

Patient information sheet: ‘It was a bit ‘sciencey” (informal caregiver 1); ‘it was long […] it took some effort to read’ (informal caregiver 2); ‘it is too complicated’ (patient-participant Inconvenience: ‘the hospital trips, we weren’t keen on the driving (px1); with all the visits, fitting it all in would have been difficult for us (informal caregiver 2).

Fear of unknown

Research process: ‘I thought that it was quite a complex study’ (patient-participant 2); ‘I thought it meant testing brand new drugs’ (patient 4).

Research team: ‘I think there is a trust thing isn’t there’ (informal caregiver 3); ‘I suppose others would be more comfortable’ (patient 3).

Caregiver workload

‘Her getting worse was a problem for me, because it would be a problem for me’ (informal caregiver 3).

‘If I got worse then he would have to help get about you see. I don’t like to ask him to do more for me’ (patient 3).