The UP-C is a manualized, cognitive-behavioral, and emotion-focused group intervention with a transdiagnostic approach aimed at the treatment of emotional problems (i.e., anxiety and depression) in children aged 7 to 12 years old. This psychological intervention mainly focuses on reducing the intensity and frequency of strong and aversive emotional experiences in children through the development of skills that allow them to face these emotions in a more adaptive way.

By targeting the factors common to emotional disorders (avoidance, emotional reactivity, affective intolerance) we believe this intervention might increase the effectiveness of the treatment of these difficulties (mainly in the cases where comorbidity is present). It may also contribute to therapists' expertise when dealing with different emotional disorders, by not requiring the simultaneous mastery of multiple interventions, to a reduction of costs associated with training and to the planning of more individualized and flexible interventions. This approach could help to make interventions suitable for a set of problems more accessible to the public - which is particularly relevant to the Portuguese context. Thus, to better adapt to the limitations existent in mental health services in Portugal, a modified version of the UP-C was developed by reducing the number of sessions for parents.

The current study seeks to understand whether this adapted version of the UP-C - the UP-C/C - less demanding in terms of resources required for its application, is effective in reducing children's emotional symptomatology and produces changes on maladaptive parenting strategies used by parents. This version is mostly centered on the child, who participates in 15, 90 minutes, group sessions. In this version of the program, the parents adopt the role of "cotherapists", and support homework completion at home by the child. They also have access to psychoeducational material (in video and written format). Additionally, the UP-C/C includes three parental sessions that focus on parenting strategies shown to be useful in challenging situations. This study also seeks to evaluate child and parent involvement in the intervention and understand its predictors.

These are the specific objectives of the study:

1. To evaluate the efficacy of the UP-C/C through a Randomized Controlled Clinical Trial with two conditions (UP-C/C and Coping Cat in group format) on the primary outcomes (child's anxiety and depression symptoms, interference of anxiety and depression in the child's school, social and family functioning), secondary (quality of life, emotional expression and cognitive errors), and on the transdiagnostic factors (avoidance, emotional reactivity, affective intolerance) and on the parental variables (parents' emotional behaviors, orientation towards the child's emotions, symptoms of anxiety and depression);
2. To evaluate the involvement of the child and parents in the program (attendance, dropout, active participation) and find out its predictors (age; intensity of symptoms; readiness for change; therapeutic alliance; expectations regarding the intervention).

The main hypothesis of the study, relating to the efficacy study, is the following:

- UP-C/C is expected to have equivalent results to Group Coping Cat in outcomes related to anxiety and quality of life and superior results in outcomes related to depression and transdiagnostic mechanisms.

Participants will be recruited from schools located in Lisbon's metropolitan area (Portugal). The selection of participants will be carried out through a two-phase screening, after parental consent and assent from the children are obtained. In both phases, the children will complete a questionnaire that assesses symptoms of anxiety and depression. Children whose score in the screening of anxiety symptoms is in a percentile equal to or greater than 80 will be selected at both assessment times. Families of children selected through the screening are invited to an individual assessment session. In this session, a brief set of questions to parents is asked to ensure their child's eligibility, and current difficulties are explored in more detail. If the necessary criteria are met, the pre-intervention evaluation processes take place (child and caregivers complete a set of measures).

To access the efficacy of the UP-C/C, this intervention will be compared with a cognitive-behavioral intervention previously shown to be effective in the treatment of anxiety disorders, the Coping Cat program in a group format. Thus, once the recruitment and evaluation of eligibility criteria is finished, the children and their parents will be randomly allocated to one of two conditions:

1. experimental group (i.e., children and parents who benefit from the UP-C/C program);
2. control group (i.e., children who benefit from the Coping Cat, group format).

In both conditions, 15/16 weekly sessions with the children will take place in groups of 5 to 7 participants. Therapist's and children's manuals are available. The groups will be conducted by clinical psychologists integrated in the research team. All therapists received training to conduct the intervention and will receive weekly supervision by the project supervisor. Every session will be observed and evaluated by an external observer through a checklist.

Regarding the primary and secondary outcomes, transdiagnostic mechanisms and parental variables, the study includes 5 assessment times - at pre-intervention, 6 weeks after the start of the intervention, after the intervention ends and at two follow-ups, 3 and 6 months after the end of the intervention. The variables related to the therapeutic process are evaluated at each session (active participation, assessment of program conduction, therapeutic alliance) and in the 1st session (readiness for change). Informed consent, from the parents and the children, will be sought at each assessment time. Consent protocol includes a paragraph, that explains how data will be recorded and who has access to it. Only information relevant to the study is collected.

For the analysis of the effects of the intervention, a multivariate analysis of variance (MANOVA) (SPSS 26.0) will be used. To assess participants' engagement in the UP-C/C, data will be collected from all sessions and percentages of attendance and dropout will be calculated. ANOVA analysis of variance and Chi-Square tests (SPSS 26.0) will be used to examine differences between the Experimental Group and the Control Group in attendance/active participation and dropout, respectively. To explore predictors of attendance/active participation and dropout Multiple Regressions and Logistic Regressions (SPSS 26.0) will be used, respectively.

Assuming a mean effect size of 0.4 on improvement in depressive symptomatology, an alpha=0.05, and power=0.8, for a 2-group design with 5 repeated measures, the total sample size required is 80 (G*Power). Given an expected dropout of 17%, it will be necessary to recruit a minimum of approximately 94 children. Thus, a sample of 47 children in the experimental group and 47 in the control group is expected. 7 UP-C/C groups with a maximum number of 7 children will be conducted. To allow for a satisfactory number of participants, the therapeutic groups will be carried out in two periods (March 2023 to July 2023 and October 2024 to February 2024).

Missing data due to participant's dropout will be handled by intention-to-treat principles, estimated using the last observation carried forward (LOCF) method.

Inclusion Criteria:

• Children aged 7-12;
• Children whose score in the screening of anxiety symptoms is in a percentile equal to or greater than 80;
• Speaking, reading and understanding Portuguese;

Exclusion Criteria:

• Diagnosis of a psychotic disorder, bipolar disorder, intellectual disability or autism spectrum disorder;
• Severe current suicidal/homicidal ideation;
• The child is being subjected to a not yet stable dose of a psychotropic or other type of medication (i.e., modified less than 1 month prior to baseline assessment);
• The child or parents are not fluent in the Portuguese language;
• The child is benefiting from another psychological intervention;
• Presence of the parents and the child cannot be guaranteed in most of the intervention and assessment sessions; the presence of the parents is only required in the parenting sessions and in the evaluation sessions (week 6, after the intervention, and two follow-ups).