Betrayed by the nervous system: a comparison group study to investigate the 'unsafe world' model of selective mutism

The study presented in the following verifies some assumptions of the novel 'unsafe world' model of selective mutism (SM). According to this model, SM is a stress reaction to situations erroneously experienced via cognition without awareness as 'unsafe'. It assumes a high sensitivity to unsafety, whereby the nervous system triggers dissociation or freeze mode at relatively low thresholds. We examine whether there is a correlation between SM, sensory-processing sensitivity and dissociation. We compared a sample of 28 children and adolescents with SM (mean age 12.66 years; 18 females) to 33 controls without SM (mean age 12.45 years; 21 females). Both groups were compared using a medical history sheet, the 'Selective Mutism Questionnaire' (SMQ), a 'Checklist for Speaking Behaviour' (CheckS), the 'Highly Sensitive Person Scale' (HSPS), the 'Child Dissociative Checklist' (CDC), the 'Adolescent Dissociative Experience Scale' (A-DES) and the 'Social Phobia and Anxiety Inventory for Children' (SPAIK). Appropriate parametric and non-parametric tests were conducted to examine differences between groups. The results indicate that sensory-processing sensitivity was significantly higher in the group of children and adolescents with SM [X²(1) = 7.224, p = 0.0007; d = 1.092]. Furthermore, dissociative symptoms were more common in children and adolescents with SM than in controls [F(1, 33) = 13.004, p = 0.001; d = 0.986]. The results indicate that sensory-processing sensitivity and dissociation are important factors of SM that may hold important implications for the treatment. TRIAL REGISTRATION: This study is registered with the ClinicalTrials.gov number NCT04233905.