Selective mutism (SM) is a complex anxiety disorder characterized by an inability to speak in certain social situations. People with selective mutism are fully capable of speaking and understanding language just as well as those without SM, but they become completely unable to communicate in anxiety-provoking social situations.

For example, a child with SM may communicate perfectly well at home but remain silent at school, even when a teacher or classmate speaks directly to him/her. It is important to note that SM is not an act of disrespect or defiance. Those with the disorder wish to speak but simply cannot. They become so overwhelmed that they are unable to verbally express themselves, even when their silence will result in embarrassment, punishment or shame. Most people with SM are also highly sensitive, and this may contribute to feelings of over-arousal.

SM is typically a childhood disorder, but in some severe cases, it may persist into the teen and adult years. Before a diagnosis of SM is given, other disorders that can hinder communication must be ruled out, such as autism, stuttering or hearing loss. Social anxiety almost always co-occurs with SM. In fact, the disorder itself is considered by some experts to be a type of avoidance strategy for severe social anxiety.

There are varying degrees of severity in SM with each person exhibiting different behaviors and reactions. For example, while all people with SM become mute in certain social situations, some will appear social and even participate in activities, while others appear quite distressed and cannot participate in any form of activity or non-verbal communication, such as eye contact. Furthermore, some children might speak only with peers but not teachers, while others might speak only with teachers but not peers.

Symptoms of SM typically lessen over time, but in some rare cases, the disorder may become progressively worse. When this occurs, it is called progressive mutism, and it may become so severe that the sufferer cannot even speak with loved ones.

Example: Katie, a playful and chatty child at home, would become uneasy and painfully quiet every time she walked into her kindergarten classroom. When another child tried speaking to her, she would hang her head in silence. Although it took nearly six months to overcome her selective mutism, she eventually began to assimilate and make friends.