The participants will be adolescent (11-17 years) and adult (>18 years) clients presenting with common non-severe mental health problems who seek mental health services at the Centro de Psicología Aplicada. The CPA is an outpatient psychological service where students of the last semesters of the Clinical Psychology degree develop and practice their psychological care skills as co-therapists of professional clinical psychologists.

The CPA provides outpatient psychological services to individuals: children, adolescents and adults, couples and families. At the CPA, care is carried out through the co-therapy model, which involves the participation of a professional clinical psychologist and a trainee. Psychotherapists with diverse theoretical and clinical backgrounds (mainly psychodynamic, cognitive, systemic and integrative), but a common constructivist approach, work in the center. The following elements are transversal in their practice: therapeutic alliance, healing environment, and a collaborative procedure between the client, the psychotherapist and the trainee co-therapist.

The CORE-OM (Evans et al., 2002) is a 34-item self-report instrument designed for use in heterogeneous services and based on a pan-theoretic core of psychological distress, including subjective well-being, problems, risk, and functioning. Items are scored on a scale from 0 (never) to 4 (always or almost always). Higher scores indicate greater psychological distress. This instrument is suitable as an initial assessment tool and as an outcome measure. The Spanish versionof this measure will be used. This version was translated by Feixas et al. (2012) and has shown good psychometric properties in Spain (Trujillo et al. 2016) and Ecuador (Paz et al. 2020).

The CORE-10 (Barkham et al., 2013) is a generic, short, and easy-to-use assessment measure. Its items were drawn from the CORE-OM. The CORE-10 is an instrument that has shown good psychometric properties (Barkham et al., 2013) and is practical for use on a session-by-session basis with people presenting with psychological distress in mental health settings. Its Spanish version will be used (Feixas et al., 2012).

The YP-CORE is a brief self-report instrument capable of detecting psychological distress in adolescents, generated by a wide range of problems, while providing information about the person's general functioning (Twigg et al., 2009). It has 10 items, which must be answered on a 5-point scale (0 to 4). Its Spanish version will be used. The YP-CORE was translated to Spanish by Feixas et al. (2018) and showed adequate psychometric properties. In the present study, we will use a version of this measure adapted for Ecuador and Latin America whose psychometric properties are being explored.

It is a 10-point scale that asks respondents to rate their degree of satisfaction with life in the present. It will be presented in Spanish.

The CORE TAF is a pragmatic form designed to be filled out by therapists at baseline. The CORE-TAF includes referral information, sociodemographic data on the client, and data on the nature, severity, and duration of the client's problems. (Barkham et al., 2015; Evans 2003). We will use its Spanish version, which is currently being translated.