196 Anxiety Disorders
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 select ive mutism are almost always given an addi-
tional diagnosis of another anxiety disorder—most commonly, social anxiety disorder (so-
cial phobia).
Prevalence
Selective mutism is a relatively  rare disorder and has not been  included as a diagnostic cat-
egory in epidemiological studies of prevalen ce 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 individual s 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.
Development and Course
The onset of selective mutism is usually befo re age 5 years, but the disturbance may not
come to clinical attention until entry into scho ol, where there is an increase in social inter-
action and performance tasks, such as readin g 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. 
Risk and Prognostic Factors 
Temperamental. Temperamental risk factors for sele ctive mutism are not well identi-
fied. Negative affectivity (neuroticism) or be havioral inhibition may play a role, as may