What is selective mutism? What are the characteristics, causes, comorbidities and treatments? Eva Billstedt looks at this diagnosis.
What is selective mutism?
Selective mutism (SM) is a condition characterised by an inability to speak in specific social situations (e.g. at school) even when one is able to speak in other situations (e.g. at home or with a single classmate). This inability should not be attributable to language deficits or communication disorders as in cases of autism or psychotic disorders. The disorder must have been prevalent for at least one month and brought about deteriorated functioning at school/work and in interpersonal relationships.
SM tends to initially manifest in preschool, but is typically only identified as a problem upon entering elementary school, most likely due to the increased demands placed on performance and social interaction at that time. Prevalence numbers shift between 0.11 and 2 percent depending on the population studied and the criteria used. In a Swedish study by Kopp and Gillberg (1997), the prevalence among school children was found to be 0.18 percent. Research has indicated a somewhat uneven gender distribution, with a higher proportion of girls than boys. The estimated gender distribution (girl:boy) varies between 2.6:1 and 1.5:1.
In the previous diagnostic manual DSM-IV, selective mutism was included in the chapter on other disorders in toddlers, children and adolescents. In the new manual DSM-5, SM was instead included among anxiety disorders. This new categorisation of the diagnosis highlights an increased focus on underlying social anxiety problems. In clinical groups, children with SM are often described as anxious, shy, sensitive, clingy and needy. On the other hand, there are also accounts of children with SM being passive-aggressive, stubborn, oppositional and controlling (Dummit, Klein, Tancer, 1997).
The etiology behind SM is yet to be determined, but it is believed to be multifactorial with both environmental and genetic background factors. Similar symptoms are often present in the individual’s family, which speaks to the likely significance of genetic factors, but bilingualism (a clear environmental factor) is also often considered to increase the risk of SM. SM also comes with an increased risk of other comorbid conditions like anxiety disorders, particularly social phobia but also separation anxiety and other phobias. In addition, more and more recent studies have demonstrated links between SM and developmental disorders affecting communication, learning, motor skills etc.
A medical record study we did found that 63 percent of a clinical SM group (n=97) had also been diagnosed with autism/autism spectrum disorders when examined for such conditions (Steffenburg, Steffenburg, Gillberg, Billstedt et al. 2018). Kristensen’s study from 2000 also describes an increased risk of autism in cases of SM. We also found that the SM group with concurrent autism had later onset of SM symptoms, that they were diagnosed with SM at a higher age, that they more frequently had a history of delayed speech development, and that a higher proportion of this group suffered from learning difficulties compared to the group that only had SM.
A small number of studies have examined different treatment methods. The available research on this subject includes two literature reviews (Cohan, Chavira & Stein, 2006; Östergaard 2017), both of which primarily support cognitive behavioural therapy with multimodal intervention efforts like relaxation exercises, social skill training, cognitive restructuring etc. There is less support for medical treatment (only a few studies) and this is recommended only in more severe cases of SM. These days, medical treatment of SM typically employs selective serotonin reuptake inhibitors (SSRI).
The few long-term follow-ups that have been done show that although the SM symptoms tend to lessen over time, communication difficulties and social anxiety often linger into childhood