Diagnosing selective mutism: a critical review of measures for clinical practice and research

Selective mutism (SM) is an anxiety disorder (prevalence 1-2%), characterized by the consistent absence of speaking in specific situations (e.g., in school), while adequately speaking in other situations (e.g., at home). SM can have a debilitating impact on the psychosocial and academic functioning in childhood. The use of psychometrically sound and cross-culturally valid instruments is urgently needed. The aim of this paper is to identify and review the available assessment instruments for screening or diagnosing the core SM symptomatology. We conducted a systematic search in 6 databases. We identified 1469 studies from the last decade and investigated the measures having been used in a diagnostic assessment of SM. Studies were included if original data on the assessment or treatment of SM were reported. It was found that 38% of published studies on SM reporting original data did not report the use of any standardized or objective measure to investigate the core symptomatology. The results showed that many different questionnaires, interviews and observational instruments were used, many of these only once. The Selective Mutism Questionnaire (SMQ), Anxiety Disorders Interview Schedule (ADIS) and School Speech Questionnaire (SSQ) were used most often. Psychometric data on these instruments are emerging. Beyond these commonly used instruments, more recent developed instruments, such as the Frankfurt Scale of SM (FSSM) and the Teacher Telephone Interview for SM (TTI-SM), are described, as well as several interesting observational measures. The strengths and weaknesses of the instruments are discussed and recommendations are made for their use in clinical practice and research.