Selective Mutism: The Fraternal Twin of Childhood Social Phobia.

Background: Selective mutism (SM) is an anxiety disorder with a close link to childhood social phobia (SP). Our studies compare behavioral problem profiles in children and adolescents with SM and SP and control groups and assess the comorbidity patterns of SM and SP.

Methods: Participants aged 3-18 years with SM (n = 95), SP (n = 74) and internalizing disorders (INT, n = 46) and a typically developing control group (CG, n = 119) were assessed with the Child Behavior Checklist (CBCL); adolescents were additionally assessed with the Youth Self-Report (YSR). Comorbidity was assessed in SM and SP participants with a diagnostic interview.

Results: SP was detected in 94% of children with SM. SM participants showed different behavioral and psychiatric symptoms than SP: they were more frequently affected by lifetime separation anxiety disorder (SM: 45%, SP: 26%) and oppositional defiant disorder (SM: 22%, SP: 5%), and less by generalized anxiety disorder (SM: 6%, SP: 20%) and major depression (SM: 12%, SP: 26%). Adolescents with SM showed high rates of agoraphobia (SM 27%; SP 10%) and more social problems (YSR), and were more withdrawn (CBCL, YSR) than those with SP alone. Specific behavioral problems of SM and SP compared to INT and CG were observed.

Conclusion: SM and SP represent separate but closely related disorders, distinct from other INT and CG, with specific patterns of lifetime comorbidities.