Group Version of the UP-A in a Spanish Public Mental Health Setting.

The Revised Child Anxiety and Depression Scale-30 (RCADS-30; Sandín et al., 2010) at pre, post-intervention and 3, 6 and 12 months follow-up.

Range from 0 to 90. Symptoms of anxiety (panic disorder, social phobia, separation anxiety disorder, generalized anxiety disorder, and obsessive-compulsive disorder) and depressive disorders symptoms.

Higher scores mean a worse outcome.

Parents completed the "parent version" of the RCADS.

Depression and Anxiety Interference Scale for Children and Adolescents EIDAN (Espinosa et al., 2022) . It is a 10-item self-reported instrument that evaluates the interference of emotional symptoms in the adolescent's daily functioning in the previous weeks, in several contexts (school, family and with peers). The higher the score, the higher the level of interference. Assessed at pre, post-intervention and 3, 6 and 12 months follow-up.

Range from 10 to 40. Parents completed the "parent version" of the EIDAN.

The adolescent version of the Top Problem Assessment (TPA) (Ehrenreich, 2018; adapted from Weisz et al., 2011) was used to enhance treatment outcomes and strengthen the therapeutic alliance. Adolescents were asked to write down the issues that concerned them the most and assess the severity of each problem by rating its impact on daily functioning on a scale from 0 ("not a problem at all") to 10 ("very, very much a problem"). Each adolescent selected between one and three problems and evaluated their severity at five time points: at the beginning of the program (session 3), mid-treatment (session 8), the final session (session 16), and during follow-ups at 3, 6 and 12 months.

Emotion Regulation Strategies Questionnaire CERE-II (Sandín et al., 2008). Adapted to Spanish by Sandín et al. (2008).

Evaluates 7 subscales of the "emotion regulation" construct at pre, post-intervention and 3, 6 and 12 months follow-up.

Higher scores in maladaptive regulation strategies (supression; rumination; distraction) and lower scores in adaptive strategies (attention/awareness/understanding; acceptance/tolerance; cognitive reappraisal; self-instructions) mean a worst outcome

The Depression Questionnaire for Children and Adolescents [Cuestionario de Depresión para Niños y Adolescentes] (CDN; Sandín et al., 2016) at pre, post-intervention and 3, 6 and 12 months follow-up.

Range from 0 to 48. Depressive symptoms. Higher scores mean a worse outcome.

The Children Positive and Negative Affect Schedule [Escalas PANAS para niños y adolescentes] (PANASN; Sandín, 2003) at pre, post-intervention and 3, 6 and 12 months follow-up. Positive and negative affect. Range 10-30. Higher scores of negative affect and lower scores os positive affect mean a worse outcome.

Childhood Anxiety Sensitivity Index CASI (Silverman et al., 1991) ; Spanish adaptation by (Sandín et al., 2002). Anxiety sensitivity at pre, post-intervention and 3, 6 and 12 months follow-up.

Range 18 to 54. Higher scores mean a worse outcome.

Emotional Avoidance Strategy Inventory for Adolescents EASI-A ( Kennedy & Ehrenreich-May, 2017) ; Spanish adaptation by (García-Escalera et al., 2016). Emotional avoidance strategies at pre, post-intervention and 3, 6 and 12 months follow-up.

Range 0 to 68. Higher scores mean a worse outcome.

Satisfaction with Life Scale SWLS (Diener et al., 2010; adapted to Spanish by Sandín et al., 2015).

Evaluates satisfaction with life at pre, post-intervention and 3, 6 and 12 months follow-up. Range 5 to 20. Lower scores mean a worse outcome.

Adolescent Relationships Scales Questionnaire ARSQ (Scharfe, 1999) ; adapted to Spanish by (Magaz et al., 2011). The ARSQ is an instrument composed of 17 self-reported items, which allows obtaining scores for the three types of attachment identified in the theory of Bartholomew (1990) and Bartholomew and Horowitz (1991): secure attachment, fearful/preoccupied attachment, and avoidant attachment. Evaluates attachment styles at pre, post-intervention and 3, 6 and 12 months follow-up.

Higher scores in insecure attachment styles (fearful/preoccupied attachment, and avoidant attachment) and lower scores in secure attachment style mean a worst outcome.

Somatic Symptoms Scale extracted from the PHQ-15, Patient Health Questionnaire (adapted from the patient health questionnaire - physical symptoms - PHQ-15; (Kroenke et al., 2002) ; Extracted and translated from the APA website - DSM-5 Level 2 Cross -Cutting Symptom Measures). It is composed of 13 items that evaluate somatic symptoms in adolescents between 11 and 17 years old at pre, post-intervention and 3, 6 and 12 months follow-up. Range 0 to 26. Higher scores mean a worse outcome.

The Clinician Severity Rating CSR (ADIS-IV Interview; Silverman et al., 2008). This scale indicates, for each main and secondary diagnosis, the clinician's estimate of severity according to the following scale from 0 to 8: 0 = no seriousness, 1 - 2 = little disturbance/no disabling, 3 - 5 = clear disturbance/disabling (at least a 4 is required for diagnosis) 6 - 7 = high/disabling disturbance; 8 = very serious/disabling disturbance. Assessed at pre and post-treatment.

The Children's Global Assessment Scale CGAS (Schaffer et al., 1983; version translated into Spanish by the Xunta de Galicia Agreement and the University of A Coruña Foundation, 2012). It is a clinician-estimated measure of the adolescent's overall level of functioning in the last month. Scores range from 100-91 (optimal functioning in all areas) to 10-1 (constant need for supervision).

Evaluates General Functioning at pre, post-intervention and 3, 6 and 12 months follow-up.

The Clinical Global Impression (Severity) Scale CGI-S (Guy, 1976) . Using this scale, the clinician estimated the severity of the adolescent's anxiety and depression symptoms. Scores will range from 1 ("Normal, not at all ill"), to 7 ("Extremely ill").

Evaluated at pre, post-intervention and 3, 6 and 12 months follow-up.

The Clinical Global Impressions (Improvement) Scale CGI-I (Guy, 1976) . This scale was completed by the clinicians during post-treatment and follow-ups. The adolescent's improvement was scored on a scale from 1 to 7, with 1 being "very much improved" and 7 being "very much worse".

Assessed at post-intervention and 3, 6 and 12 months follow-up.

In the post-treatment evaluation, adolescents and involved parents completed a 12-item questionnaire that evaluates satisfaction with the program and the quality of the relationship with the therapist (Sandín et al., 2020).