I would like to think of Selective Mutism (SM) as a side effect of severe social anxiety. Some people may have panic attacks when they are in extremely uncomfortable situations, but if you look at some of the symptoms of panic attacks (increased heart rate, trouble breathing, blurred vision, etc) they vary among different people. Selective Mutism is kind of the same. Along with sweating, increased heart rate, etc. they also develop an inability to speak in uncomfortable situations or when around certain people. They are physically unable to speak. Someone with SM has no more control over their ability to speak than they would their heart rate. Regardless of the list of symptoms they can all be traced back to anxiety.
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