We were sent a question about selective mutism and loss of speech. Selective mutism is defined as an anxiety condition in which a person with normal verbal skills is unable to speak in particular settings. For those without an intellectual disability, this is typically described in children but can also occur in adults. In our experience, it seems likely that this is more common in adults with Down syndrome (DS) than it is in people without DS.
The person who sent the question noted that the definition of selective mutism may be limiting in people with DS, some of whom already have a degree of impaired communication. We agree that this is not clear cut and there are several issues to consider. It is likely that this answer will not completely clarify the use of the term (diagnosis) selective mutism in people with DS but hopefully it will add information to the discussion about various communication differences. One of the challenges is that there is likely some overlap and even co-occurrence of the conditions discussed below. In addition, some or many people with DS will have difficulty explaining how they are feeling and, lacking this self-report of the individual, there will be some speculation as to what the cause is.
People with DS tend to have better receptive language (what they hear) than expressive language (what they say). That needs consideration whenever discussing issues of language and communication for people with DS. Interestingly, many families report that their loved one with DS has better expressive language skills when the person is self-talking. We think that when the social pressure to speak in front of others is not present (for example, when self-talking) the person is able to speak more clearly. Feeling social pressure may lead to a learned behavior of avoiding verbal expression as in the example of Bill below.
This scenario of Bill is a very common one in our office. In the course of the history portion of an appointment, I ask Bill, a 23-year-old man with DS and his family some questions about his health. Bill repeatedly turns to his parents and defers to them to answer the questions. Even when I ask his parents not to answer, Bill points to his parents and insists that I ask them. He does not speak during the appointment despite his parents reporting he is quite verbal at home and able to function and communicate quite well in most social settings. However, when asked questions in a medical appointment, he defers to his parents.
Health questions are challenging and not ones he can easily answer. He has learned in other medical settings that, if he defers to his family or delays in answering, the person asking the questions will turn to his family. He has learned how to "get off the hot seat." He knows that his dysarthria (articulation impairment) can make it challenging for him to get his point across, and it is easier to defer to his parents. Rather than having selective mutism, this seems to be more of a learned behavior. With coaching and assisting, Bill is usually able to participate in the office discussion to some degree. I find sometimes that if the person is struggling to answer I will reassure him and then ask him if he can answer just a few questions. Then, if he still prefers, I will ask additional questions of his parents. Bill may then be willing to answer a few questions despite his discomfort.
Social Anxiety Disorder
Depending on the level of anxiety that Bill is experiencing in the office setting, another possible cause or diagnosis is social anxiety disorder, which is a common type of anxiety disorder. A person with social anxiety disorder feels symptoms of anxiety or fear in certain or all social situations. In the example above, if Bill gets quite anxious in the office due to feeling he is not able to answer the questions appropriately, it may be social anxiety. Since his symptoms include not speaking, he may also have selective mutism. It is estimated that 90% of children who have selective mutism also have social anxiety (among people without an intellectual disability, selective mutism is most commonly diagnosed in children).
In some individuals, rather than not speaking at all, the change in speech is that the person will only whisper and will not speak in a normal volume. In some individuals with DS, the mutism is not selective. These individuals won't speak in any setting. Using the term "selective" doesn't seem appropriate, but it does appear to be very similar to selective mutism but extends broadly to most or all social settings.
Treatment of selective mutism may require multiple specialty providers. A psychologist, other mental health provider, or speech therapist may provide a variety of therapies. Medications to reduce anxiety may also be prescribed. Additional information about medications can be found at this link and this link. The therapies may include some social skills training to promote more comfort with speaking in social situations.
Other Causes of Loss of Speech
Selective mutism has also been described with obsessive compulsive disorder. We have seen a decrease in speech or only whispering in individuals we have diagnosed with "obsessional slowness," which is described further in this resource. In obsessional slowness, the individual moves very slowly in many, most, or even all aspects of their life. In addition, typically the individual has significant compulsive behavior which often manifests as repetitive rituals. Lack of speaking or only whispering are common symptoms as well and, in our experience, it commonly occurs in many or all settings rather than selectively. There are some authors who question whether obsessional slowness is a real diagnosis and instead think a different diagnosis should be given. Whether obsessional slowness is or is not a true diagnosis in people without DS, there are clearly some people with DS who develop symptoms that seem best described as obsessional slowness.
Additionally, some individuals who develop regression have decreased speech. Catatonia may be a symptom or cause of regression and some individuals with catatonia only whisper or don't talk. This is commonly observed in most or all settings and not selective in our experience.
One difference between obsessional slowness and regression is that it seems people with regression have lost skills while commonly, in obsessional slowness, the individual can still do the skill (e.g., speaking) but doesn't do it or does it exceedingly slowly.
People with DS may have a decline in skills including speech for a variety of other reasons, too. Further information is available at this link. In older individuals with DS, Alzheimer's disease will likely cause a decline in speech capabilities at some point in the disease.
People with DS may have a decrease in expressive language beyond the impairment that is common in DS. Assessing and treating for causes in further impairment of expressive language should be undertaken to improve expressive language and, if possible, return it to the previous level.