Selective mutism is a severe anxiety disorder where a person is unable to speak in certain social situations, such as with classmates at school or to relatives they do not see very often.
It usually starts during childhood and, if left untreated, can persist into adulthood.
A child or adult with selective mutism does not refuse or choose not to speak at certain times, they're literally unable to speak.
The expectation to talk to certain people triggers a freeze response with feelings of panic, like a bad case of stage fright, and talking is impossible.
In time, the person will learn to anticipate the situations that provoke this distressing reaction and do all they can to avoid them.
However, people with selective mutism are able to speak freely to certain people, such as close family and friends, when nobody else is around to trigger the freeze response.
Selective mutism affects about 1 in 140 young children. It's more common in girls and children who are learning a second language, such as those who've recently migrated from their country of birth.
Experts regard selective mutism as a fear/phobia of talking to certain people. The cause is not always clear, but it's known to be associated with anxiety.
The child will usually have a tendency to anxiety and have difficulty taking everyday events in their stride.
Many children become too distressed to speak when separated from their parents and transfer this anxiety to the adults who try to settle them.
Some children have trouble processing sensory information such as loud noise and jostling from crowds – a condition known as sensory integration dysfunction.
This can make them "shut down" and be unable to speak when overwhelmed in a busy environment. Again, their anxiety can transfer to other people in that environment.
There's no evidence to suggest that children with selective mutism are more likely to have experienced abuse, neglect or trauma than any other child.
Another misconception is that a child with selective mutism is controlling or manipulative, or has autism. There's no relationship between selective mutism and autism, although a child may have both.
The main warning sign is the marked contrast in the child's ability to engage with different people, characterised by a sudden stillness and frozen facial expression when they're expected to talk to someone who's outside their comfort zone.
They may avoid eye contact and appear:
More confident children with selective mutism can use gestures to communicate – for example, they may nod for "yes" or shake their head for "no".
But more severely affected children tend to avoid any form of communication – spoken, written or gestured.
Some children may manage to respond with a few words, or they may speak in an altered voice, such as a whisper.
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