The understanding of SM as an anxiety disorder related to shyness, social anxiety and inhibited temperament has increased in popularity over the last decade. Reports of children with SM indicate that most are shy, inhibited and anxious. These reports combined with clinical experience suggest that SM may be the manifestation of an inhibited temperament, or inborn personality of mood (Dow et al., 1995). There is some evidence that there is a genetic link between children with SM and anxious parents or family members. Most commonly, social phobia, avoidant personality disorder, and parents with a history of SM themselves were more prevalent in families with a child with SM than those without (Black & Uhde, 1995; Chavira et al., 2005; Kristensen, 2001). In addition, most children with SM also have one or more other anxiety disorders, especially social phobia (Black & Uhde, 1995; Dummit et al., 1997). Other common comorbid anxiety disorders include separation anxiety disorder, generalized anxiety disorder and specific phobias (Dummit et al., 1997).

Behaviorally inhibited children may also have a decreased threshold of excitability in the almond-shaped area of the brain called the amygdala. The amygdala receives and processes signals of potential threat and sets off a series of reactions that will help individuals protect themselves. In anxious individuals, the amygdala seems to overreact and set off these responses even when the individual is not really in danger. In the case of SM, the anxiety responses are triggered by social interactions and settings where speaking is expected including school, the playground or social gatherings. Although there may be no logical reason for the fear, the feelings that the child with SM experiences are just as real as if an actual threat or danger were present.

Other factors may also contribute to the development of SM. A significant number of children with SM also have expressive language disorders and some come from bilingual family environments (Kristensen, 2000; Elizur & Perednik, 2003). While these factors do not cause SM, they can contribute to a child’s anxiety with speaking. The child may become more self-conscious about his or her speaking skills and may have increased fear of being judged negatively by others.

A stressful environment may also be a risk factor in the development and maintenance of SM. Although earlier reports of SM suggested that a history of abuse and trauma may be associated with the development of SM, there is no evidence that there is a causal relationship between trauma and SM (Black & Uhde, 1995). However, if significant stressors are present, they may contribute to the SM by exacerbating the child’s already present anxiety.