Effectiveness of selective serotonin reuptake inhibitors in inpatients with selective mutism compared to social anxiety disorder: an observational study

Selective Mutism (SM) is a rare childhood anxiety disorder characterized by a persistent inability to speak in specific social settings despite adequate speaking ability in others, sharing etiological and clinical overlap with Social Anxiety Disorder (SAD). While evidence for pharmacological treatment in SM is limited, selective serotonin reuptake inhibitors (SSRIs) have demonstrated potential efficacy, but studies on effectiveness in routine clinical practice are lacking. This single-center, retrospective observational study analysed data from 2011 to 2021 on children aged 4-14 years with SM or SAD treated as inpatients at a German university hospital. The mean age at admission was 11.9 years in both groups. Using propensity score matching and statistical modelling, we compared SSRI prescription patterns, dosage, and duration of inpatient/day-care treatment (DOT) between groups. In the SM group, we additionally tested for differences in speaking pattern at discharge comparing children with and without SSRI medication. SSRI treatment was more frequent in SM (75.4%) than in SAD (55.0%, p = 0.011). Adjusted for pattern of additional internalizing, externalizing and specific developmental disorders, no main effects of group (SM versus SAD), nor of SSRI treatment or dosage between and across groups were found on DOT. In the SM group, SSRI treatment was associated with more strongly improved speaking pattern at discharge compared to treatment without SSRI (p = 0.009). Results are discussed in relation to optimal dosage and effectiveness of SSRI treatment on improved speaking pattern in SM.