Table 2.

Inclusion and exclusion criteria within the PICOS framework.

PICOS	Inclusion	Exclusion
Population	Adult participants experiencing psychological difficulties or displaying maladaptive coping behaviours indicative of underlying psychological difficulties (e.g. self-harm).	Non-adult samples not experiencing psychological difficulties. This includes: • Parents/carers of children diagnosed with a clinical physical/mental health condition. • Healthcare workers, school teachers or other professionals in healthcare, education or social care.
Intervention	Compassion Focused Therapy delivered in a group format, covering the primary components, which derive from the work of Paul Gilbert (2, 28, 29). These primary components include: ○ Psychoeducation such as on the concept of compassion, the three regulatory affect systems, ‘tricky brain’, fears of compassion, the role of shame and self-criticism ○ Exercises such as compassionate letter writing, compassionate attention, soothing rhythm breathing.	Other compassion-based interventions (e.g., compassion cultivation training, Mindful Self-Compassion). • Mindfulness-based interventions, whereby the focus is primarily on mindfulness rather than the core compassion therapy components as identified in the inclusion criteria. Studies that looked at CFT where there was significant variation from standard protocols such as culturally-adapted CFT (30). Compassion-focused therapy delivered in a 1:1 format.
Comparison (Types of qualitative data collection and analysis)	Recognised qualitative methods of data collection (e.g., focus groups, qualitative interviews) and analysis [e.g., interpretative phenomenological analysis [IPA; (31)], thematic analysis (32), and content analysis (33)].	Non-standard qualitative methods of data collection or analysis methods of analysis that were unreferenced (e.g., ‘a qualitative analysis was performed’ or ‘themes were extracted’ with no reference provided).
Outcome (phenomenon of interest)	Service user experiences and perceptions of CFT interventions.	Studies where service users/participants were asked to compare their experiences of CFT with other psychological interventions.
Study Design	Qualitative studies or mixed methods pilot/feasibility studies.	Studies using only quantitative methodologies. Grey literature including conference abstracts, reports, government documents.