This revision: 26th April 2013 .
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Selective mutism (SM) is a psychiatric disorder in which a person who is normally capable of speech is unable to speak in given situations or to specific people.
Selective mutism usually co-exists with shyness or social anxiety. In fact, many children diagnosed with selective mutism also have social anxiety disorder (100% of participants in two studies and 97% in another.)
Some researchers therefore speculate that selective mutism may be an avoidance strategy used by a subgroup of children with social anxiety disorder in order to reduce their distress in social situations.
A child with selective mutism may be completely silent at school for years but speak quite freely or even excessively at home. There is a hierarchical variation among those suffering from this disorder: some people participate fully in activities and appear social but don't speak, others will speak only to peers but not to adults, others will speak to adults when asked questions requiring short answers but never to peers, and still others speak to no one and participate in few, if any, activities presented to them.
In a severe form known as "progressive mutism", the disorder progresses until the sufferer no longer speaks to anyone in any situation, even close family members.
Selective mutism is by definition characterized by the following:
- Consistent failure to speak in specific social situations (in which there is an expectation for speaking, e.g., at school) despite speaking in other situations.
- The disturbance interferes with educational or occupational achievement or with social communication.
- The duration of the disturbance is at least 1 month (not limited to the first month of school).
- The failure to speak is not due to a lack of knowledge of, or comfort with, the spoken language required in the social situation.
- The disturbance is not better accounted for by a communication disorder (e.g., stuttering) and does not occur exclusively during the course of a pervasive developmental disorder, schizophrenia, or other psychotic disorder.
The incidence of selective mutism is not certain. Based on the number of reported cases, the figure is commonly estimated to be 1 in 1000, 0.1%. However, a 2002 study in The Journal of the American Academy of Child and Adolescent Psychiatry estimated the incidence to be 0.71%.