Children who refuse to speak in situations where talking is expected or necessary, to the extent that their refusal interferes with school and making friends, may suffer from selective mutism.
Children suffering from selective mutism may stand motionless and expressionless, turn their heads, chew or twirl hair, avoid eye contact, or withdraw into a corner to avoid talking.
These children can be very talkative and display normal behaviors at home or in another place where they feel comfortable. Parents are sometimes surprised to learn from a teacher that their child refuses to speak at school.
The average age of diagnosis is around 5 years old, or around the time a child enters school; most parents report that their children's symptoms begin years earlier.
From the Selective Mutism Group: To meet diagnostic criteria, the child or adolescent with selective mutism shows significant impairment in daily functioning, typically in educational or occupational settings, and by refraining from social participation at school and other settings due to a pronounced fear of speaking. Most affected children and adolescents function normally in other ways and learn age appropriate skills; however, some may have other comorbid anxiety disorders, developmental delays such as impaired social skills, and communication disorders.