Helen, an 11-year-old girl with autism, goes to mainstream school and does very well at all the subjects. But no one at school has ever heard her speak. She used to sit quietly in the classroom rocking her body and seems oblivious to everybody around her. However, her written work is always neat and correct.
Her mother says she talks to her family at home, always whispering, but only if there is nobody else present there. If the family’s friends come to visit, she turns into ‘a silent statue’, never uttering a word.
Helen can speak loudly but only if she is alone in her room. Her mother listens to these one-way conversations from behind the door with tears in her eyes: ‘Why does she talk to the empty room about whatever’s happened at school, and never ever talk to us like this? She can talk, can’t she? Why can’t she talk all the time?’
Helen’s ability to speak seems to be affected by the stress of strangers being present and any unfamiliar environment.
In 1934, a Swiss child psychiatrist Moritz Tramer described the case of an 8-year old child who didn’t speak in certain situations but spoke in others. To emphasize the lack of verbal contact as a conscious choice (the boy “refused” to speak), Tramer introduced the term ‘elective mutism’.
In early American diagnostic criteria 'elective mutism’ was used to define ‘refusal to talk’ in social situations. This ‘conscious will to withdraw’ from verbal contact was seen as oppositional defiance, not as social anxiety. In the DSM-IV (1994) and DSM-V (2013) the term ‘elective mutism’ was replaced with ‘selective mutism’ (SM) to reflect the fact the person is unable to talk in certain social situations. In both DSM-V, and ICD-11, it was moved from “disorders of childhood and adolescence” to “anxiety disorders”. It means that SM can be diagnosed in children, adolescents and adults, provided that it is a type of anxiety disorders, not a symptom of psychosis, developmental, neurological or speech disorders.
Selective mutism is an anxiety disorder, characterized by an inability to speak in specific social situations despite speaking normally in other situations.
SM usually starts in early childhood, between age 2 and 8. It is often first noticed when the child starts to interact with people outside their family, such as when they begin nursery or junior school. If SM is left untreated, it can persist into adulthood.
SM is more common in girls, with a gender ratio 2:1 (McInnes et al. 2004).
A prevalence rate is about 1–2% (Sharp et al., 2007). It may be higher among children with speech and language delays (Manassis et al. 2003). Bilingual children have much higher rates of SM; and higher rates of SM exist in communities with many ethnic minorities or immigrant families (Krysanski 2003).
SM is a heterogenic group of disorders with a multifaceted, overlapping, and complex aetiology (Rozenek et al. 2020).
There is a continuum of SM severity: from children with mild impairments to children with very severe symptoms. Children on the mild end of the spectrum may be able to speak to certain individuals but remain mute with others. They may be able to respond when a direct question is asked of them, perhaps in a quiet voice with fleeting eye contact, but struggle to initiate a conversation verbally. Children with a more severe presentation may be unable to speak to anyone in a school setting or a public place; they may have difficulty talking to family members whom they see often. Some children at the more severe end of the spectrum may even have difficulty responding and/or initiating communication nonverbally (Kotrba 2015).
There have been attempts to identify distinct groups in SM. For instance, Cohan et al. (2008) distinguish three different subgroups of children with SM:
exclusively “anxious” children with SM, demonstrate freezing behaviour, difficulty with both nonverbal and verbal responding and initiating, and significant social anxiety. The severity of SM in this group is the lowest.
“anxious/oppositional” children demonstrate defiant behaviours (running away, active avoidance, stubbornness and/or controlling behaviour), specifically when prompted to speak or engage.
“anxious/communication-delayed” children exhibit mild to severe communication delays along with clinically significant social anxiety. They may have expressive and/or receptive language delays. The severity of SM in this group is the highest.
SM can co-occur with social anxiety disorder, separation anxiety disorder, or phobias. About 75% of children with SM may also have subtle differences in hearing and processing that can negatively impact their ability to talk (Muchnik 2013). Communication difficulties are common in this population as well and may be especially prevalent among those with sensory and anxiety problems (Mulligan et al. 2015).
SM and ASD
There is evidence that SM and ASD can co-occur (e.g., Rozenek et al. 2020; Muris & Ollendick 2021). Steffenburg et al. (2018) found that 63% of their SM study group had a comorbid ASD (no gender difference). The SM group with combined ASD had later onset of symptoms, higher age at diagnosis, more often a history of speech delay, and a higher proportion of borderline IQ or intellectual disability. Others have noted similar features of autism among children with selective mutism (Cengher et al. 2020; Suzuki et al. 2020). The results highlight the risk of overlap between ASD and SM.
There are two main trends in common treatment of SM: (1) pharmacotherapy used to treat anxiety disorders and (2) behavioural (contingency management, social skills, stimulus fading and modelling) cognitive behavioural therapy (CBT: the identification of anxious thoughts that may contribute to the mute behaviour and teaches the child to identify negative thoughts and coach the children to replace thee with positive thoughts instead). However, there are a few data on the effectiveness of both forms.
As SM is heterogeneous, the outcome is variable (Hua and Major, 2016). The severity and the type of comorbidities may complicate the situation and determine the final effects of the therapy (Holka-Pokorska et al. 2018). The earlier a child is diagnosed, (and the treatment starts) the better the overall prognosis is. Many children overcome SM completely with proper treatment.
What is it like to have SM?
Walker and Tobbell (2015) present the experience of five people with SM (one of them was the study co-author Aaron Walker who has largely overcome his selective mutism and who provides his own reflections from diary extracts). The researchers report how “selective mutism was experienced… as the imprisonment of a true identity behind silence and how they have attempted to negotiate their unwanted identities of being selectively mute.”
They identified several key themes, such as, for example, the sense of separation from their mutism, as it was NOT a part of their true identity, e.g.:
“It isn’t me. I know who I am and I’m not shy or quiet, maybe that makes it harder. When I’m with my parents I can be myself but around everyone else it’s like [selective mutism] takes over. I can get the words in my head but something won’t let me say them and the harder I try the more of a failure I feel like when I can’t.” (Hannah, aged 26, diagnosed at age 17)
and their feelings of regret for a wasted life, their lament for the ‘normal life’ they had missed out on, e.g.:
“A lot of the time I worry about things I haven’t done, that I should have… I could have gone to university, I always did well at school… Maybe I’d have been able to get a job and be in a relationship. A lot of the time I imagine what my life would be like if I didn’t have selective mutism.” (Lily, 23, diagnosed at the age of 12)