A study by Melfson et al. investigating the extent of social anxiety in individuals with different mental disorders, of which one studied group included children with severe Selective Mutism using SPAIK (Social Phobia and Anxiety Inventory), the German version of SPAI-C.

The study found that subjects with Selective Mutism scored lower on the SPAIK scale compared to subjects with diagnosed Social Phobia; Hence, Melfson's results appear to be contradictory to the classification of SM as a manifested symptom of severe social anxiety.

Melfson suggested that if SM were a symptom of severe social anxiety, the SPAIK scores of those with SM and those with social phobia should have been in a similar range.