A crucial diagnostic element of selective mutism (SM) is that the child has the ability to both comprehend spoken language and to speak, but yet fails to do so in select settings. Children with SM persistently lack the ability to speak in some settings (for example, school) but not in others (for example, home). In most children, SM is a passing phase and the ability to communicate in all settings is regained by adulthood. SM may, however, continue throughout adolescence or prevent the young person from acquiring age-appropriate social skills.