Anxiety Disorder of Childhood

The goal of this clinical trial is to evaluate a smartphone based just-in-time adaptive intervention (JITAI) tool to deliver somatic behavioral recommendations for anxiety management among youth. The main questions it aims to answer are: * Is the JITAI tool acceptable among the adolescent study population? * Is the JITAI tool feasible to deliver to the adolescent study population? * Does the study support preliminary efficacy of the JITAI tool among the adolescent study population? The tool will be pilot-tested among a sample of 50 rural adolescents experiencing elevated anxiety levels who will be randomly assigned to the JITAI tool or a waitlist control, for a treatment period of 3 months. Participants will be asked to: * Use the smartphone based JITAI tool which will deliver somatic behavioral recommendations intended to manage anxiety levels for a treatment period of 3 months * Respond to the tool's prompts on a daily basis and follow the delivered behavioral recommendations * Complete anxiety and interoception assessments at study start, study end (3 months), and one-month follow-up * Complete usability and user experience instruments at study end (3 months)

Selective mustism (SM) is an anxiety disorder that manifests in childhood. Children with Children with SM do not speak in certain social situations where this is expected of them. For example, a child may talk at home, but is afraid to speak at school. The goal of this clinical trial is to determine the efficacy of behavioral therapy for children with selective mutism (SM) combined with virtual reality (VR) homework exercises. Virtual Reality Exposure is an effective treatment for adults with anxiety disorders. The main questions to answer are: * Is behavioral therapy combined with VR homework exercises effective in the treatment of SM? * Which familial factors contribute to a positive treatment outcome and homework adherence? A single-case experimental design (SCED) will be used to evaluate the efficacy of the treatment. The child's speaking behavior at baseline will be compared to the child's speaking behavior in the different phases of the intervention. Participants will: * Follow individual therapy sessions at school. * Practice with the VR homework exercises at least once a week. * Parents and teachers will evaluate the child's speaking behavior.