Objective: This study was carried out to determine the prevalence of selective mutism (SM) in an urban school population and to assess comorbidity and family characteristics.

Method: Teachers of primary schools, teaching children between the ages of four and 12, were sent a description of SM and asked to complete the selective mutism questionnaire (SMQ) if they believed a child in their class met criteria. Thirty-nine schools were sampled, covering a catchment area of 10,927 children. Children who screened positive on the SMQ were offered a full psychiatric assessment. Parent, child and clinicians completed various rating scales.

Results: A response rate of 100% from schools was obtained. The prevalence rate of SM was 0.18% (20/10927). fourteen (70%) attended for further evaluation. All children scored within the clinical range on the Clinical Global Assessment Scale (CGAS), indicating moderate to severe impairment. fifty percent (7) reported a family history of social anxiety disorder, and 43% (6) autistic spectrum disorders.

Conclusion: This is the first Irish based prevalence study of SM. Results indicate that SM is not as rare as previously believed. Children with SM were found to have significant functional impairment along with a strong family history of anxiety and autism.