Selective Mutism is best thought of as a specific phobia of speaking. For some children, this generalizes to other types of communication, including nonverbal gestures and writing. However, children with SM have a predisposition to anxiety disorders in general (genetically and biologically), so it is not uncommon for kids with SM to also demonstrate other types of anxiety, worry, or inhibition. For example, around 90% of kids with SM also have Social Phobia or a fear of being the center of attention and being judged.

It is extremely uncommon to see a true onset of SM in adolescents since the trajectory of SM is a lifelong genetic predisposition to anxiety as well as biological indicators of anxiety (e.g., an overactive amygdala). Thus, kids who have SM tend to be anxious and inhibited from very early on in life.

It is possible that a child could have anxiety and inhibition but function within the realm of “normal” development for some time. For example, a child could be quiet and “shy” but respond if directly spoken to. This would not call great attention to the child. It is possible that this same child, who already demonstrated some anxiety but hasn’t quite passed the threshold to true Selective Mutism, could have an experience that results in emotional distress and increased anxiety, as well as mutism. A school move, a difficult interaction with a teacher, or an embarrassing public interaction could result in more shutting down verbally, thereby moving the adolescent from anxiety/inhibition to diagnosable Selective Mutism.

Anxiety is believed to be the cause of Selective Mutism, although kids with SM don’t always directly report that they feel “anxious” about speaking. Research suggests that kids with SM do have a genetic predisposition to anxiety as well as an overactive amygdala (our brain’s “guard dog,” which alerts us to potential danger and engages the body’s fight/flight/freeze response). Evidence-based interventions do exist for SM and show very promising outcomes. Specifically, behavioral interventions based in desensitization (including stimulus fading, shaping, and reinforcement), as well as changes in the way that others interact with the child, can be very useful in treating SM. My book, Overcoming Selective Mutism, goes into great detail and has useful worksheet pages for effectively treating kids with Selective Mutism. Additional treatment information can be found on the Selective Mutism Association’s website, www.selectivemutism.org.

https://www.amazon.com/Overcoming-Selective-Mutism-Parents-Field/dp/1732599602

Generally, children with SM can speak well (in a developmentally appropriate manner) in the home setting. Some portion of children with SM do have language delays (typically expressive-language delays) that can complicate diagnosis, but these children usually speak more readily in the home setting (albeit with expressive language delays) and less readily in the school/social setting. Thus, the diagnostic difference could be the prevalence of speech in different settings, as opposed to the quality of speech.

Differentiation between SM and autism can be challenging, especially for individuals who do not see the child in comfortable situations. First, while kids with SM might present with some characteristics of ASD in public (e.g., poor eye contact, lack of speech, stiff body movements/posturing, etc.), they lack these characteristics when engaging in comfortable settings with family. Parents may wish to take a video of the child speaking in the home setting and show it to the school staff or psychologist to provide an example of the child under “comfortable” conditions.

If further evaluation is needed, a psychologist could provide testing specific to ASD, such as an ADOS or ADI-R; however, scores may be skewed by SM symptoms, and this should be taken into consideration when determining a diagnosis.

The very nature of SM is its “selectivity”, meaning that children with SM speak to some individuals and not to others. Some children with SM feel much more comfortable speaking to peers and do not speak to adults outside of their immediate family. Others speak to adults but have more hesitancy with peers. This could be because (1) there is more of a cultural expectation that children will answer an adult’s direct question, so there is some social pressure to speak to adults that doesn’t exist for speaking to peers or (2) adults may be more “predictable” to interact with than peers….adults tend to be more engaging, less overtly judgemental, and have control of the conversation (starting and ending it successfully) in comparison to peers.

Children with SM can certainly be taught non-verbal communication tools, including sign language or using PECs (picture exchange cards). This can be helpful in increasing overall communication for a child who does not communicate at all in necessary settings. However, we must be aware that these tools can later be used as a “crutch” to verbal communication. If we teach a child to get every need met with nonverbal means, will they be motivated to use verbalizations later?

The best use for nonverbal communication tools is as a steppingstone for severe cases of SM (where the child does not communicate at all in necessary settings, such as school). We may decide to teach sign language or allow the child to type on a computer, but with the intent to eventually move from accepting nonverbal communication to expecting verbal communication to get needs met.

We are not certain why SM is observed more in girls than in boys. A few hypotheses include:

1. There is a greater expectation for girls to speak in social situations as opposed to boys, and therefore it stands out more when a girl does not speak. For example, when girls play, there is a lot of conversational back-and-forths (e.g., playing house, animating dolls, etc.). When boys play, there is less of a need for conversational speech (e.g., sports, active games). Additionally, research shows that girls ask more questions and are called on more in elementary school by teachers.
2. Women are more likely to be diagnosed with an internalizing disorder (such as anxiety) at any age in comparison to men (who are more likely to be diagnosed with an externalizing disorder). Thus, this difference in prevalence may demonstrate real gender-based differences in mental health issues.