DSM-IV-TR estimates that SM affects 1 in 1000 children referred for mental health treatment (APA, 2000). However, several researchers have suggested that the true prevalence of SM in the general population is largely underestimated (Bergman et al., 2002; Hayden, 1980; Hesselman, 1983; Kupietz & Schwartz, 1982; & Thompson, 1988). Recent studies show that SM is not as rare as it was previously believed to be but is comparable to other, widely known disorders of childhood. A study targeting a large sample of children in a Los Angeles, CA school district identified children who met the diagnostic criteria for SM and found a prevalence rate of 7.1 per 1,000 children (Bergman et al., 2002). A subsequent study in Israel found an almost identical prevalence rate (Elizur & Perednik, 2003). These numbers suggest that SM has a higher prevalence than autism (.5 per 1000), major depressive disorder (.4 to 3 per 1000), Tourette’s disorder (.5 per 1000), obsessive-compulsive disorder (.5 to 1 in 1000) and other well-known disorders. In comparison to other studies, which only accounted for diagnosed cases of SM, provides evidence that a large number of individuals with SM are undiagnosed or misdiagnosed. Parents of children with SM who enter treatment often report that their child was misdiagnosed with autism or another pervasive developmental disorder, mental retardation or oppositional-defiant disorder. Most are told (if anything) by uniformed professionals that there is nothing wrong with their child, that their child is “just shy,” or will grow out of this behavior. Thus, the lack of awareness among educators and treating professionals leads to delays in diagnosis and missed opportunities for treatment.
SM is slightly more common in females than in males. Although the duration of SM often lasts for several months, left untreated, it may sometimes persist longer and may continue for several years (APA, 2000). The average age of onset is 5 years, even though most parents report that their children’s symptoms began years earlier (Leonard & Dow, 1995). In his treatment of children with SM, Thompson (2000) found that children who establish speech in previously mute settings before age eight typically become verbal in school and social settings within one year. Children who demonstrated longer-term mutism were likely to continue their silence into upper grades and into adulthood (Thompson, 2000). While reports of older children and adolescents with SM are scarce, based on our collective clinical experience, individuals who to enter into treatment later may suffer from depression and other disorders in addition to SM but can make treatment gains and overcome SM without it continuing into adulthood.