Associated features of selective mutism may include excessive shyness, fear of social em- barrassment, social isolation and withdrawal, clinging, compulsive traits, negativism, temper tantrums, or mild oppositional behavior. Although children with this disorder generally have normal language skills, there may occasionally be an associated commu- nication disorder, although no particular association with a specific communication dis- order has been identified. Even when these disorders are present, anxiety is present as well. In clinical settings, children with selective mutism are almost always given an addi— tional diagnosis of another anxiety disorder—most commonly, social anxiety disorder (so- cial phobia).
Selective mutism is a relatively rare disorder and has not been included as a diagnostic cat— egory in epidemiological studies of prevalence of childhood disorders. Point prevalence using various clinic or school samples ranges between 0.03% and 1% depending on the set- ting (e.g., clinic vs. school vs. general population) and ages of the individuals in the sample.
The prevalence of the disorder does not seem to vary by sex or race/ethnicity. The disor- der is more likely to manifest in young children than in adolescents and adults.
The onset of selective mutism is usually before age 5 years, but the disturbance may not come to clinical attention until entry into school, where there is an increase in social inter- action and performance tasks, such as reading aloud. The persistence of the disorder is variable. Although clinical reports suggest that many individuals ”outgrow” selective mutism, the longitudinal course of the disorder is unknown. In some cases, particularly in individuals with social anxiety disorder, selective mutism may disappear, but symptoms of social anxiety disorder remain.
Temperamental. Temperamental risk factors for selective mutism are not well identi- fied. Negative affectivity (neuroticism) or behavioral inhibition may play a role, as may parental history of shyness, social isolation, and social anxiety. Children with selective mutism may have subtle receptive language difficulties compared with their peers, al- though receptive language is still within the normal range.
Environmental. Social inhibition on the part of parents may serve as a model for social reticence and selective mutism in children. Furthermore, parents of children with selective mutism have been described as overprotective or more controlling than parents of chil- dren with other anxiety disorders or no disorder.
Genetic and physiological factors. Because of the significant overlap between selective mutism and social anxiety disorder, there may be shared genetic factors between these conditions.
Children in families who have immigrated to a country where a different language is spo- ken may refuse to speak the new language because of lack of knowledge of the language.
If comprehension of the new language is adequate but refusal to speak persists, a diagno— sis of selective mutism may be warranted.
Functional Consequences of Selective Mutism
Selective mutism may result in social impairment, as children may be too anxious to en- gage in reciprocal social interaction with other children. As children with selective mutism mature, they may face increasing social isolation. In school settings, these children may suffer academic impairment, because often they do not communicate with teachers re- garding their academic or personal needs (e.g., not understanding a class assignment, not asking to use the restroom). Severe impairment in school and social functioning, including that resulting from teasing by peers, is common. In certain instances, selective mutism may serve as a compensatory strategy to decrease anxious arousal in social encounters.
Communication disorders. Selective mutism should be distinguished from speech dis- turbances that are better explained by a communication disorder, such as language disorder, speech sound disorder (previously phonological disorder), childhood-onset ﬂuency disorder (stuttering), or pragmatic (social) communication disorder. Unlike selec- tive mutism, the speech disturbance in these conditions is not restricted to a specific social situation.
Neurodevelopmental disorders and schizophrenia and other psychotic disorders.