Selective mutism is very often the result of a retained infantile fear paralysis reflex, which is triggered, as the name indicates, by fear, so there is certainly an anxiety component, but it is also a physiological response that makes speech impossible while the reflex is activated.
Thanks, another one I had not heard about. My daughter did not show any signs of social anxiety or any other fears until she woke up from her sleep one night at 18 months. Both the sleep issues and social anxiety came out of no where and went from non-existent to extreme at this time.
