Table 12 Key concept: purpose–based systematic case studies

1. Representative cases of a broader clinical population (typicality);

2. Descriptive cases that capture specific psychotherapy processes as they emerge in treatment (particularity);

3. Unique cases due to unusual variations that go beyond the ‘average’ population (deviation);

4. Critical cases that test existing theories (faslficiation/confirmation);

5. Exploratory cases that indicate a beginning phase of a multiple case study research (hypothesis generation);

6. Transferable cases that seek to aggregate and transfer case study findings onto other cases (generalisability).