Background
Selective mutism is defined by the Diagnostic and Statistical Manual of Mental Health Disorders, 5th Edition (DSM-5) as “an anxiety disorder, given that a large majority of children with selective mutism are anxious.” [1]
Selective mutism is a disorder in which an individual is not able to speak aloud in specific situations when there is an expectation of conversational speech. [1] Communicative language is generally intact in such individuals, although selective mutism can coexist with language and communication disorders.
Selective mutism can be accompanied by other anxiety disorders such as separation anxiety disorder, social anxiety disorder (formerly called social phobia), agoraphobia, and panic disorder, as well as by shyness and anxiety; however, it can also exist without other anxiety-related disorders. [2]
Selective mutism generally occurs by age 5 years; however, usually it is not diagnosed until the child starts school. In some cases, adolescents and adults continue to experience an inability to speak in public. This inability is generally most disabling at school, as the child cannot be assertive and speak when called on by teachers. In adults, functional impairment occurs when public speaking or lecturing is required in one's vocation. Often, the child with selective mutism designates a friend or close family member to serve as an interpreter of communication and whispers into that person's ear, so that communication occurs with the designated person as intermediary.
Often, selective mutism can coexist with social phobia, also known as social anxiety, and is defined by marked and persistent fear of social or performance situations in which embarrassment may occur; exposure to the social or performance situation almost always causes an anxiety reaction such as a situationally bound or situationally predisposed panic attack.
Selective mutism can also be the precursor to agoraphobia and/or panic disorder. Agoraphobia is a specific phobia in which the individual fears being in crowded places. People with agoraphobia often become homebound. Panic disorder can result in significant disability and iatrogenically induced illness, especially in situations when invasive medical testing is done, because the severity of symptoms such as chest pain and palpitations and medical testing can intensify the severity of the panic symptoms.
The anxiety reaction is not due to psychosis; individuals are able to recognize their fears as excessive and unreasonable. However, the ability to fully comprehend that the reaction is out of proportion to the precipitant may be less complete in children and may depend on their cognitive-developmental level of functioning due to deficits in emotional regulation. Recent studies have looked at physiological measures reflecting the severity of anxiety. Children with selective mutism were compared with children with social phobia in a study of 35 children (average age, 8 y). Those with social phobia and selective mutism had chronically higher levels of arousal as reflected by respiratory sinus arrhythmia and skin conductance levels. This may help explain why children with selective mutism may appear to others to not be overtly anxious; their silence may serve to decrease outward signs of anxiety observable by others. [3]
Studies that use physiological measures to objectively measure the severity of anxiety have shown that children with selective mutism and social anxiety as compared with children with social phobia alone have chronically higher levels of arousal (more intense anxiety) as reflected in the presence of respiratory sinus arrhythmia and skin conductance levels. Children with selective mutism may appear to others to not be overtly anxious, especially because of their silence, as their anxiety is not directly observable by others. [3]
Selective mutism significantly impairs the individual's level of functioning, as the individual is unable to complete required educational, social, and family tasks, and the emotional distress engendered in situations requiring the person to speak out loud can result in school refusal. [4]
Selective mutism is a disorder that first occurs in childhood and can continue into adolescence and adulthood. In adults with this disorder, functional impairment occurs when public speaking or lecturing are required in one's vocation. Severe social anxiety may not be evident, as the person may actually function in a relaxed manner when using nonverbal (ie, gestures, signing) communication styles. [5]
Shyness does not necessarily persist in adolescents with social anxiety disorder. A study by Burstein et al found that almost 50% of a group rated themselves shy; however, only 12% of adolescents who identified themselves as shy actually met criteria for lifetime incidence of social anxiety disorder as measured by the World Health Organization Composite International Diagnostic Interview 3.0, and 5.2% of adolescents who did not identify as having shyness had social phobia. [6]
There is significant comorbidity of social phobia with anxiety disorders, major depressive disorder, and drug use disorders, without regard to the presence or absence of shyness. Adolescents with shyness were more likely to report agoraphobia compared with the no-shyness group. Adolescents with social phobia versus adolescents with shyness had greater impairment in the areas of school/work, family relationships, and social life; however, they were no more likely to obtain professional treatment. Eighty percent of adolescents with social phobia failed to seek or to obtain professional treatment for their anxiety, and rates of prescribed medication use were systematically low across groups: 2.3% of adolescents with social phobia and 0.9% of adolescents with shyness used paroxetine.
Adolescent gender did not have a significant effect on the prevalence of social phobia. However, culture can cause parents to underreport anxiety; a clinically referred sample of 408 parent-youth dyads of African American adolescents versus Latino and white adolescents that used the Screen for Child Anxiety Related Emotional Disorders (SCARED) found that parents tended to significantly underreport anxiety symptoms. [7]
Pathophysiology
Serotonin pathways may be involved in the mediation of the anxious and obsessive qualities of selective mutism. This theory is reinforced by animal models of phobic behavior and by response to commonly prescribed medications such as selective serotonin reuptake inhibitors (SSRIs), such as paroxetine, sertraline, or older heterocyclic-type antidepressants (eg, clomipramine [Anafranil]). [8]
Continued studies are needed to help to determine the genetics of anxiety-related negative valence system (NVS) traits (fear/threat, potential harm/anxiety, sustained threat/loss, frustrative non reward) as it continues to be challenging to identify candidate gene and Genome Wide Association Studies (GWAS). [9]
A study of 106 children with selective mutism also included 1028 young adults who completed measures of social interactional anxiety and 920 young adults with childhood behavioral inhibition. [10] The study found a nominal significance (P = .018) for association of selective mutism with rs2710102, which, with rs6944808, was part of a common haplotype associated with selective mutism (permutation P = .022). Adjusting for sex and ancestral proportion, each copy of the rs2710102*, a risk allele in the young adults, was associated with increased odds of being more than 1 standard deviation above the mean on the Social Interactional Anxiety Scale (odds ratio = 1.33; P = .015) and Retrospective Self-Report of Inhibition (odds ratio = 1.40; P = .010).
This study is very encouraging that future genome-wide association studies might reflect an association of early onset variant of social anxiety disorder and selective mutism to a susceptibility gene, contactin-associated protein-like 2 (CNTNAP2), which has been found in other studies in relation to autism spectrum disorders. rs2710102 is a possible nonrisk allele for autism spectrum disorders and specific language impairment and may also relate to handedness. [11]
Behavioral inhibition is an early childhood temperament characterized by fearful responses to novelty and avoidance of social interactions. During adolescence, a subset of children with stable childhood behavioral inhibition develop social anxiety disorder and concurrently exhibit increased error monitoring. Increased error monitoring in 7-year-olds who were characterized regarding behavioral inhibition at age 24 and 36 months prospectively predicted risk for symptoms of social phobia at age 9 years in a study of 291 children. Those high in behavioral inhibition had increased error monitoring at age 7 years, as indexed by larger (ie, more negative) error-related negativity amplitudes. In addition, early behavioral inhibition was related to later childhood social phobia symptoms at age 9 years among children with a large difference in amplitude between error-related negativity and correct-response negativity at age 7 years.
Heightened error monitoring predicts risk for later social phobia symptoms in children with high behavioral inhibition. Research assessing response monitoring in children with behavioral inhibition may refine our understanding of the mechanisms underlying risk for later anxiety disorders and the possible need for prevention efforts. [12]
Adolescents with early-life behavioral inhibition, similar to adolescents with social phobia, did not have striatal sensitivity to valence or self-reported affective sensitivity to incentive magnitude, which supported specificity in features of generalized anxiety disorder relative to social phobia or behavioral inhibition. Distinct striatal subregion responses showed a more generalized pattern of striatal response in adolescents with social phobia when compared with their healthy peers, and this pattern emerged across the caudate, putamen, and nucleus accumbens. Widespread magnitude-related incentive activations had underlied psychological states common to behavioral inhibition and social phobia, such as performance monitoring or sensitivity to feedback and caudate hyperactivation in social phobia, and behavioral inhibition suggested anomalies in goal-based processes, which were more strongly modulated in the caudate rather than in the putamen or nucleus accumbens. [13]
Two efferent feedback pathways to the auditory periphery may play a role in monitoring self-vocalization: the middle-ear acoustic reflex (MEAR) and the medial olivocochlear bundle (MOCB) reflex. In selective mutism compared with a group of normally developing control children, a significantly higher proportion of selective mutism children had abnormal MEAR and MOCB function (58.6% and 38%, respectively) compared with controls (9.7% and 8%, respectively). The overall prevalence of abnormal MEAR and/or MOCB function was significantly higher in the selective mutism group (71%) compared with controls (16%). [14]
Epidemiology
Frequency
The average age of onset of all anxiety disorders is 11 years, which reflects that anxiety disorders are common in children and adolescents.
In the National Comorbidity Survey-Replication-Adolescent Supplement, an epidemiologic sample of 10,123 adolescents in the United States, prevalence estimates for the different anxiety disorders were as follows: generalized anxiety disorder, 2.2%; social phobia, 9.1%; specific phobia, 19.3%; panic disorder, 2.3%; and separation anxiety, 7.6%. [15]
Social phobia is the third most common mental health disorder after depression. [16] Bergman et al (2002) reported that the prevalence rate of selective mutism was 0.71% but ranged from 0.08% to 1.9% depending on the population studied. [17]
Selective mutism is seen in fewer than 1% of children observed in mental health settings and is reported about 2–2.5 times more often in females than in males. The onset of selective mutism usually occurs during the preschool years, however often it is not diagnosed until the child attends school. The diagnosis of selctive mutism often can be misdiagnosed as oppositional defiant disorder because of the significant features of oppositionality and defiance that frequently accompany the child's refusal to speak especially in the school setting. With increased chronological age, a significant percentage of children "outgrow" the selective mutism however some children continue to have difficulty with public speaking and exhibit sparse language production compared with their age mates. [18]
Mortality/Morbidity
Generally, mortality does not result directly from selective mutism, except in cases of associated major depression resulting in suicide or reaction to medication treatment (sudden cardiac death with imipramine or clonidine) or adverse reaction such as newly onset suicidality following therapy with SSRIs or other antidepressants. A high morbidity rate is observed, with many missed school or workdays; the child often develops associated school refusal because of the anxiety associated with being asked to speak in class. [18]
There is a potential risk of iatrogenically induced illness in situations in which there is severe physical symptoms of panic disorder due to the likelihood that invasive medical testing might be performed if symptoms include palpitations or chest pain. [19]
Sex
Selective mutism is diagnosed more often in females than in males, with a female-to-male ratio of about 2-2.5:1. [17]
Age
Onset of selective mutism may occur as early as school age but generally occurs by mid adolescence following a childhood history of social inhibition or excessive shyness. [2]
The onset of selective mutism is often abrupt, occurring after a stressor or humiliating social experience and typically occurs when a child first attends school (either kindergarten or preschool). Over time, anxiety levels tend to increase as children do not "grow out of" selective mutism. [20] Selective mutism persists as low self-confidence, shyness, and discomfort in social situations, often persisting into adulthood when speaking in public is required. [21]
Prognosis
The prognosis of selective mutism is fair to good and depends on the severity of impairment of functioning associated with avoidance of social situations and public speaking and on the presence or absence of secondary gain factors that tend to discourage persons from changing their adaptation to anxiety.
Perhaps related to the higher incidence of associated speech and language disorders, children who have social phobia when they are younger than 10 years have a better long-term prognosis. Prognosis is poorer in children older than 12 years who have social phobia than in younger children. Long-term prognosis is perhaps related to the implications of having fewer overall communication skills in social settings or with peers for long-term social skills and language skills development. Also, the baseline problems that provoke the adolescent have the potential to be more long-standing and more serious.
Prognosis is also considered worse if there is a family history of selective mutism. [22]
Patient Education
Parental involvement including appropriate interventions as early as in the first session can increase effectiveness of the treatment of selective mutism as well as the provision of school-based delivery of CBT. A five-year follow-up study of 30 youth found that 21 were in remission and five years later 21% of the group continued to have persistent symptoms implying chronicity of this disorder. [22]
