Selective Mutism (SM) is a childhood social communication disorder in which children consistently fail to speak in select situations, despite the ability to understand and to use language. Children with SM usually speak to family members at home, but do not speak at kindergarten or school. The speech patterns of each SM child vary along a continuum of severity – from children who speak to everyone outside school, and select peers in school, through children who fail to speak to everyone in school, peers and staff. Some will not speak to anyone outside their home, or to only certain family members inside their home, and a rare few do not speak to family members inside the home.
When another condition exists which accounts for the failure to speak, such as PDD, retardation, psychosis or a lack of language skills, then the child does not have SM.
There are many comorbid constellations of traits that have been found in research to be associated with SM, again, each child has a unique set of characteristics. Research has found that 90% of children with SM suffer from social anxiety, and 30 – 40% has some language or speech impairment. Other comorbid conditions could include: shyness and hypersensitivity, oppositional behavior, stubbornness and perfectionism, nuero-developmental delay (often auditory processing delay), and learning disabilities.
There is often a genetic component of shyness or a history of SM in one of the parents or siblings, bilingualism, or disconnectedness from the cultural milieu of the outside society.
Often there is a marked contrast between the outgoing and communicative child at home, and the inhibited, introverted functioning at school. No link has been found between intelligence and SM and no link has been found in the large research studies between traumatic events and SM. (For a sensitive, anxious child, seemingly everyday events may be experienced as traumatic – such as being shouted at by a teacher, being embarrassed in front of a class, or being mocked by peers for a mispronunciation).
Most research has found that the incidence of SM is around 0.07% that is seven children in every 1,000, and it is 3 times that number in children from bilingual homes. It is most prevalent between the ages of 4 and 8; onset usually occurs when the child first enters an educational framework in which speech is expected, but sometimes onset is gradual – the child decreases speech output until he eventually stops speaking.
The DSM –IV states that SM can be diagnosed after one month during which the child fails to speak, not including the first month at school during which his initial reticence is not necessarily the forbearer of SM.