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.
