The incidence of selective mutism refers to the number of new cases identified in a specified time period. Prevalence is the number of individuals who are living with selective mutism in a given time period. Accurate population estimates of selective mutism have been difficult to ascertain due to the relative rarity of the condition, differences in sampled populations, variations in diagnostic procedures (e.g., chart review, standardized assessment), and the use of different diagnostic criteria (Busse & Downey, 2011; Sharkey & McNicholas, 2008; Viana, Beidel, & Rabian, 2009).
- Recent prevalence estimates for selective mutism primarily range between 0.47% and 0.76% (Viana et al., 2009), although rates as low as 0.02% (Brown & Lloyd, 1975) and as high as 1.9% (Kumpulainen, Räsänen, Raaska, & Somppi, 1998) have also been reported.
- Selective mutism appears to affect more females than males by a ratio of about 1.5–2.5:1 (Cunningham, McHolm, Boyle, & Patel, 2004; Dummit, Klein, Tancer, Asche, Martin, & Fairbanks, 1997; Kumpulainen et al., 1998). However, equal ratios among girls and boys have also been reported (Bergman, Piacentini, & McCracken, 2002; Elizur & Perednik, 2003).
- Selective mutism affects approximately 1% of children being seen in behavioral health settings (American Psychiatric Association [APA], 2000).
- Higher prevalence rates have been noted in immigrant children and in language-minority children than in nonimmigrant children. Accurate diagnosis of selective mutism in these populations can be difficult due to the initial nonverbal stage (i.e., "silent period") common to second language learners (Elizur & Perednik, 2003; Steinhausen & Juzi, 1996; Toppelberg, Tabors, Coggins, Lum, & Burger, 2005).