Specific questionnaires will be used to assess specific illness interferences for the different medical conditions included in the study: the Diabetes Distress Scale (DDS; Martin et al., 2007) for participants with type I and type II diabetes; the Roland-Morris Questionnaire (Kovacs et al., 2002) for participants with low-back chronic pain; the Revised Fibromyalgia Impact Questionnaire (FIQR; Salgueiro et al., 2013) for participants with fibromyalgia; the Migraine Disability Assessment questionnaire (MIDAS; Rodríguez-Almagro et al., 2020) for participants with migraines; and the Inflammatory Bowel Disease Questionnaire (IBDQ-32; Masachs et al., 2007) for participants with inflammatory bowel illness.

Self-critical rumination Scale (SCRS; Smart et al., 2016). A 10-item questionnaire measuring self-criticism is defined as a form of negative thinking that devalues the self. It assesses thoughts that criticize the self for perceived errors, failures, weaknesses, defects, bad habits or general inadequacy. It takes into account the ruminative qualities of thought: frequency, duration, repetition, and difficulty of control. Final scores range from 10 to 40 and higher scores indicate a higher level of self-criticism.

The Depression, Anxiety and Stress Scale (DASS-21; Fonseca-Pedrero et al., 2010). This scale is an abbreviated form of the DASS questionnaire containing 21 items organized in three subscales to assess anxiety, depression, and stress symptomatology. Each subscale has 7 items that range from 0 to 3 points. Higher scores indicate higher levels of symptomatology.

The Relationships Questionnaire (RQ; Yárnoz-Yaben and Comino, 2011). This is a 4-item questionnaire designed to measure adult attachment style. The RQ consists of four paragraphs, each describing an attitude toward relationships in general. The participant rates each paragraph on a scale of 1 (does not describe me at all) to 7 (describes me exactly).

Medical Outcomes Study-Social Support Survey (MOS; Requena et al., 2007). A 20-item questionnaire that analyzes the perception of help and social support. Item 1 refers to the size of the social network and the remaining 19 items measure four dimensions of functional social support: emotional (8 items), instrumental (4 items), positive social interaction (4 items), and affective support (3 items). The items present a 5-point response scale that measures progressively (from never to always) how often each type of social support is available to the caregiver. A total score can also be obtained, where higher scores would indicate more support received.

Illness perception questionnaire - revised (IPQ-R; Pacheco-Huergo et al., 2012). The Illness Perception Questionnaire-Revised was designed to assess the cognitive and emotional dimensions of illness representations. The IPQ-R consists of three sections. Two scales measure the identity and causal dimensions and another section assesses the dimensions of duration (acute/chronic), cyclical course, consequences, personal control, treatment control, coherence, and emotional representations.

Expectancy and satisfaction questionnaire (adapted from Borkovec and Nau, 1972). A 6-item questionnaire that measures credibility towards treatment and patients' expectations of improvement. Higher score indicates higher levels of client credibility and expectation of improvement.

The Compassion Practice Quality Scale (CPQS) (Navarrete et al., 2021) has been developed to assess the key aspects of compassion practices (e.g., mental imagery, sense of connection and warmth, compassionate phrases, and compassionate gestures). This self-reported questionnaire includes 10 items that participants score on a scale ranging from 0 to 100 indicating the percentage of the time that their experience reflects each statement. Higher scores indicate higher quality of practice (i.e., less practice difficulties).

System Usability Scale (SUS; adapted from Campos et al., 2020). The System Usability Scale (SUS) provides a reliable tool for measuring the usability of a program. It consists of a 10 item questionnaire with a 5-point likert scale. Higher scores indicate higher levels of usability and client acceptance of the program.

An Ad-hoc instrument with open questions created to assess participants' opinions about the program and the support received. Adapted from Campos et al. 2018.