Intensive group treatment for children with selective mutism: A pilot multiple-baseline study

<title>Abstract</title> <p> Background Selective mutism (SM) is an anxiety disorder characterized by a persistent failure to speak in specific social situations despite speaking normally in others. Preliminary evidence suggests that intensive behavioral group interventions may be a promising treatment approach. This pilot study evaluated the effects of such an intervention for children with SM for the first time in a German clinical sample. Methods Sixteen children aged five to nine with SM participated in an intensive group intervention based on Parent-Child-Interaction Therapy for Selective Mutism (PCIT-SM). Two baseline, one post-treatment, and one three-month follow-up assessments were conducted. Primary outcome was parent-rated SM symptom severity assessed with the Frankfurt Scale for Selective Mutism (FSSM). Remission status based on a structured clinical interview served as secondary outcome. Changes over time were analyzed using linear mixed-effects models and Cochran’s Q tests. Results SM symptom severity decreased significantly over time with large effects from baseline to post-treatment ( <italic>d</italic> _{<italic>RM</italic>} = 1.03) and follow-up ( <italic>d</italic> _{<italic>RM</italic>} = 1.69). No significant differences emerged between the two baseline assessments, indicating stable pre-treatment symptom levels. Remission rates increased from 0% at first baseline to 47% at follow-up. A significant overall change in diagnostic status across assessments was observed. Exploratory analyses further indicated that general anxiety decreased from baseline to follow-up. Conclusions The findings provide preliminary support for intensive group interventions based on PCIT-SM principles as a potentially effective treatment for children with SM. Future controlled studies with larger samples and longer follow-up periods are needed to evaluate treatment mechanisms and long-term outcomes. Trial registration: German Clinical Trials Register (DRKS), DRKS00040917, retrospectively registered on 13 July 2026 </p>