Selective mutism & autism

Many autistics experience situations where they find themselves unable to speak. Often, especially in childhood, this is labeled as an anxiety-related condition called selective mutism (SM). Let’s explore the relationship between autism and SM.

What is selective mutism?

Selective mutism made its way into the anxiety disorder category of the DSM-5 back in 2013.^[1]American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington, VA (American Psychiatric Association, 2013) It is characterized by the inability to speak in certain social situations, but not others. SM occurs most often in children and therefore most people recognize SM when a child is consistently unable to speak at school or with unfamiliar adults, but has no trouble speaking at home. SM is relatively uncommon and is currently diagnosed in less than 1% of children.^[2]Children Who are Anxious in Silence: A Review on Selective Mutism, the New Anxiety Disorder in DSM-5 (Muris & Ollendick, 2015)^[3]Anxiety in children with selective mutism: A meta-analysis (Driessen et al., 2020)

What I find interesting is that even though SM is considered a form of anxiety, the diagnostic criteria does not specify anything about feeling fearful or anxious! Check out a paraphrasing of the listed criteria:

There still is no consensus about gender differences in SM. Some studies report that SM is more prevalent in children socialized as girls, but others report it is more common in children socialized as boys.^[4]Children Who are Anxious in Silence: A Review on Selective Mutism, the New Anxiety Disorder in DSM-5 (Muris & Ollendick, 2015)  Given the inconsistency, it is likely the case that there are no gender differences in SM and that these different findings are due to the specific samples that were recruited in these studies.

Research shows that individuals with SM tend to be highly anxious.^[5]Children Who are Anxious in Silence: A Review on Selective Mutism, the New Anxiety Disorder in DSM-5, Muris & Ollendick (2015)^[6]Anxiety in children with selective mutism: A meta-analysis (Driessen et al., 2020) However, unlike other anxiety disorders, like phobias for example, scientists still don’t fully understand what the underlying fears are for individuals with SM. One study found that children with SM report a wide range of fears, like social fears (e.g. meeting new people), a fear of making mistakes (e.g. saying something incorrect), language-related fears (e.g. poor pronunciation or vocabulary), and voice-related fears (e.g. the sound of their voice).^[7]Fears and fear-related cognitions in children with selective mutism (Vogel et al., 2019) This shows that, just like autism, individuals with SM are incredibly diverse.^[8]Selective Mutism: Identification of Subtypes and Implications for Treatment, Mulligan et al. (2015)^[9]The Heterogeneity of Selective Mutism: A Primer for a More Refined Approach (Kearney & Rede, 2021)

Some characteristics often associated with SM are:^[10]Anxiety and oppositional behavior profiles among youth with selective mutism (Dilberto & Kearney, 2016)

• A desire to be alone/social withdrawal
• Shyness
• Anxiety/fear/nervousness especially in certain situations like at school^[11]Distinguishing selective mutism and social anxiety in children: a multi-method study (Poole et al., 2021)
• Sudden mood changes
• Meltdowns

Social anxiety vs. selective mutism

Among all other types of anxiety, research has found a strong relationship between social anxiety and SM in particular.^[12]Anxiety in children with selective mutism: A meta-analysis (Driessen et al., 2020) Approximately 70% of children with SM also meet the diagnostic criteria for social anxiety.^[13]Children who are anxious in silence: A review on selective mutism, the new anxiety disorder in DSM-5 (Muris & Ollendick, 2015) 

Clinicians and researchers often report a difficulty in differentiating between these two anxiety-driven conditions.^[14]Can Autism Spectrum Disorders and Social Anxiety Disorders be Differentiated by the Social Responsiveness Scale in Children and Adolescents? (Cholemkery et al., 2014)^[15]Selective Mutism and Its Relations to Social Anxiety Disorder and Autism Spectrum Disorder (Muris & Ollendick, 2021) One way to differentiate between SM and social anxiety is to look at the social contexts where anxiety is experienced.^[16]Distinguishing selective mutism and social anxiety in children: a multi-method study (Poole et al., 2020) For example, individuals with social anxiety often experience their anxiety across a broad range of social interactions. In comparison, SM is usually specific to a certain social context, like school. However, it is important to keep in mind that more often than not, someone with SM also has social anxiety.

Selective mutism in adulthood

A huge gap in the SM literature is that studies are conducted almost exclusively in children. This is likely because the average age of onset for SM is between ages 2–5, and most children recover from SM within a few years.^[17]Children Who are Anxious in Silence: A Review on Selective Mutism, the New Anxiety Disorder in DSM-5, Muris & Ollendick (2015) Furthermore, while the DSM does not specify that SM is exclusive to childhood, its description refers only to childhood-related experiences like starting school for the first time.^[18]American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington, VA (American Psychiatric Association, 2013)

However, this does not mean that adults don’t experience SM. As we’ll explore down below, this is particularly true for autistic adults who may have different reasons for not being able to speak in certain situations than non-autistics.

Do autistics experience selective mutism?

Many autistics are unable to speak altogether, which does not qualify as SM. But many of us speak in a variety of contexts but have moments where we are unable to speak. So does that mean that in those cases, we also have selective mutism?

There has been some confusion over the years regarding autism and SM. Part of this confusion comes from the diagnostic criteria in the DSM-5 which states that SM behaviours cannot “occur exclusively during the course of autism spectrum disorder”.^[19]American Psychiatric Association. Diagnostic and statistical manual of mental disorders. 5th ed. Arlington, VA (American Psychiatric Association, 2013) This can be confusing because it sort of implies that autism and SM are mutually exclusive since “the course of autism” is our entire lives.

Upon closer inspection, it does clarify that they are trying to differentiate between selective mutism, where a child is able to speak in some social situations but not all, compared to a non-speaking autistic or an autistic who doesn’t speak due to social-communication difficulties unrelated to anxiety.

However, the confusion persists because current psychometrics don’t seem to be very good at differentiating between SM and autism. For example, the Social Responsiveness Scale (SRS) measures social behaviours and communication traits.^[20]Social responsiveness scale: SRS-2 (Constantino & Gruber, 2005) Using this scale, one study found that autistics and those with SM overlapped on SRS scores, showing that both populations have similar social interaction patterns which can’t always be differentiated.^[21]Can Autism Spectrum Disorders and Social Anxiety Disorders be Differentiated by the Social Responsiveness Scale in Children and Adolescents? (Cholemkery et al., 2014)

Other studies showed that there is a large overlap in those with SM versus autism and many individuals diagnosed with SM may have been missed when it comes to autism. Multiple studies have found that 63-80% of children who first received a diagnosis of SM also fit the diagnostic criteria for autism.^[22]Children with autism spectrum disorders and selective mutism (Steffenburg et al., 2018)^[23]Variations in Parent and Teacher Ratings of Internalizing, Externalizing, Adaptive Skills, and Behavioral Symptoms in Children with Selective Mutism (Klein et al., 2019)

What’s more is that there appears to be an association between autistic traits and SM traits. One study showed that in a neurotypical sample, children who had more autistic traits also had more SM traits. They even found that autistic traits can predict to a degree whether someone also has SM traits.^[24]Symptoms of Selective Mutism in Non-clinical 3- to 6-Year-Old Children: Relations With Social Anxiety, Autistic Features, and Behavioral Inhibition (Muris et al., 2021)

Research has even shown a genetic link between SM, social anxiety, and autism. The CNTNAP2 gene has been shown to be associated with an increased susceptibility for autistics to also have SM.^[25]A Common Genetic Variant in the Neurexin Superfamily Member CNTNAP2 Is Associated with Increased Risk for Selective Mutism and Social Anxiety-Related Traits (Stein et al., 2011)

Taken together, these findings suggest that there is an overlap between SM and autism. They also suggest that if an individual has SM, this may even be an indication that an autism diagnosis is worth exploring.  

One recent study theorizes that autism, social anxiety, and selective mutism can be viewed as three “allied conditions” since they frequently co-occur.^[26]Selective Mutism and Its Relations to Social Anxiety Disorder and Autism Spectrum Disorder (Muris & Ollendick, 2021) The authors of this study also are of the opinion that this explains why the traits for each condition can, at times, be difficult to distinguish from each other.

Anxious autistics

The authors are not alone in expressing difficulty with distinguishing between whether anxiety—like SM or social anxiety—is a co-occurring condition with autism, versus just a different presentation of autism.^[27]The presentation and classification of anxiety in autism spectrum disorder (Kerns & Kendall, 2012)^[28]Can Autism Spectrum Disorders and Social Anxiety Disorders be Differentiated by the Social Responsiveness Scale in Children and Adolescents? (Cholemkery et al., 2014)

My perspective is that we already know many autistics also experience anxiety.^[29]Anxiety disorders in children and adolescents with autistic spectrum disorders: a meta-analysis (van Steensel et al., 2011) We also already know that a lot of our anxiety comes from trying to navigate neurotypical social norms. What seems likely then, is that SM and/or social anxiety traits are some possible ways in which autistics express their anxiety.^[30]Selective Mutism and Its Relations to Social Anxiety Disorder and Autism Spectrum Disorder (Muris & Ollendick, 2021) For example, we may be socially anxious because we don’t understand how to interpret a given social interaction; and we may react by being unable to respond in conversation.

The thing is, if so many autistics are also anxious, I think the difficulty in the literature may stem in part from such strong adherence to a set of diagnostic criteria that were likely developed by observing the behavioural traits of anxious autistics! I wonder if the distinction would be more obvious if the DSM recognized that so many autistics have anxiety. What do you think?

Sensory overwhelm

One characteristic of autism which I don’t think is captured well in the definition of SM is that autistics may respond to sensory overwhelm by not being able to speak. For example, your brain may be so overloaded with trying to process what’s happening in your environment that you may not have the capacity to speak at the same time.

Research suggests that children who have SM and also experience sensory sensitivities are likely to also be autistic.^[31]Selective Mutism in Children With and Without an Autism Spectrum Disorder: The Role of Sensory Avoidance in Mediating Symptoms of Social Anxiety (Ludlow et al., 2022) Some researchers have also found an altered neural pathway in auditory processing as a possible explanation for the relationship between sensory processing and selective mutism.^[32]An auditory-neuroscience perspective on the development of selective mutism (Henkin & Bar-Haim, 2015)

Autistic shutdowns

Another autistic characteristic that encompasses times when we can’t speak is shutdowns. In response to overstimulation, we may reach a point where we are in crisis and we uncontrollably withdraw completely from our surroundings as a means to cope with the stress. A common feature of a shutdown is unresponsiveness or uncommunicativeness. While SM does not include any specifics about shutdowns, for us autistics, this is another instance where we may be unable to speak. This can overlap with the diagnostic criteria for SM if, for example, we find a specific social context overwhelming and consistently enter a state of shutdown in this context.

To understand the nuance between how some autistic experiences fit with the criteria for SM but others don’t, here’s an example from my life:

When I’m in the middle of a shutdown, I am completely “gone”. It often looks like I’m completely “frozen” or paralyzed. If someone tries talking to me, I can often hear them, and sometimes I am able to process what they are saying and even generate a response in my head, but no matter what, I am unable to speak. It feels like the part of my brain that controls my speech is just completely offline. For me, this isn’t consistently triggered by being in a specific context. It’s very much related to feeling generally overwhelmed. I can be in any context, alone or in a social interaction. Therefore, in my case, I experience situations where I can’t speak, but it does not technically fit with the official diagnostic criteria for selective mutism.

Do you experience times where you cannot speak? Do you find that it’s related to your anxiety/overwhelm? Is it consistent with a specific context? What does SM look like for you?

Support for selective mutism in autism

Since SM is related to anxiety, seeking support should be similar to seeking support for other forms of anxiety. For example, in autism, this might mean removing yourself from an overstimulating situation before you reach your capacity and end up in shutdown mode. It may also be helpful to identify the real or perceived fears that are associated with your anxiety-provoking context so that you can figure out what your needs are in a given situation.

Summary

• Selective mutism is a form of anxiety characterized by the inability to speak in certain contexts but not others.
• Many people who have selective mutism also experience social anxiety, and many people who have been diagnosed with selective mutism also fit the diagnostic criteria for autism but were initially missed.
• For autistics, not being able to speak in a given situation may be associated with our anxieties related to navigating social interactions, as well as our response to anxiety-provoking situations like sensory overstimulation.
• It is important to recognize that while many autistics experience moments where they cannot speak (and some autistics speak very little or don’t speak at all), you are only considered to have selective mutism if the pattern of non-speaking is consistent and context-dependent.