Several studies have been conducted on the prevalence of selective mutism. However, the subjects and methods di er between these studies, and no uni ed perspective has been achieved. e purpose of this study was to conduct a systematic investigation by school type and grade level of children with selective mutism enrolled in kindergarten, elementary school, and lower secondary school in Japan and to evaluate the prevalence of selective mutism. e overall enrollment rate for children with selective mutism, in a total of 73 public kindergartens and elementary and lower secondary schools was found to be 0.21%, with more female than male students (male-tofemale ratio=1 : 2.1). e enrollment rate by school type was the highest for kindergarten (0.66%) and slightly decreased for the higher stages of education. e percentage of schools where any children with selective mutism were enrolled (called the school enrollment rate) was 39.7% for all schools and gradually increased from kindergarten to lower secondary school (at 46.7%). In this study, the Diagnostic and Statistical Manual of Mental Disorders Fi h Edition diagnostic criteria for selective mutism were employed, and schoolteachers determined selective mutism based on the criteria. e school enrollment rate obtained in this study supports the results of other studies and provides new insights into selective mutism. e limitations of this study include an insucient number of samples and a failure to ensure adequate interpretive skill on the part of the respondents.

A person with selective mutism (SM) in adolescence sometimes reveals group adaptation di culties such as school absenteeism, as well as other associated psychopathological symptoms such as depression; and thus their condition is typically highly complex. In this study, a high school student with SM, who experienced associated symptoms of school absenteeism, social anxiety, and depression besides suppression of speech and movement, was given feedback on voice volume a er reading aloud and subjected to an in vivo exposure technique. In the voice volume feedback, as a result, the student's voice volume improved by 10 dB compared to the beginning of the study and became loud enough to be easily heard. In addition, anxiety scores on speech and activity decreased, and the number of responses to the counselors increased. However, the treatment cannot be considered adequate since the student spoke only in a low voice and less frequently even a er the treatment. Nonetheless, recovery from SM in adolescence is deemed di cult; thus, the intervention introduced in this study may be inferred to have had measurably positive e ects.

Previous studies have not fully identi ed the areas in which children with selective mutism face di culties in school and the support they are given. A survey was conducted in this study among teachers serving at di erent tiers of education (kindergarten, elementary, and lower secondary school) to ascertain the teachers' views on the extent of the di culties children with selective mutism face in-school activities, and their views on the in-school support the children require. What the di culties faced by children with selective mutism generally have in common is that they occur during activities and in settings requiring speech based on the results of this study. However, individual di erences are also shown, particularly in elementary and lower secondary schools. Indications are that support systems involving coordination inside and outside of schools are required and are presently inadequate. Better systems will be required in the future, including the use of special needs education coordinators and the assignment of experts with high levels of expertise. In addition, encouraging understanding among classmates is an e ective step despite the di culties involved, and the development of such programs should be sought. ese show that support is required to provide places where children with selective mutism can feel comfortable.