I'm not familiar with psychoanalysis. But I suppose that in the past selective mutism was thought to be neurosis, and that was the reason why past theories about the etiology of selective mutism focused on family pathology. In psychodynamics approach, it is thought that children who were brought up in pathological families have the risk of creating conflict. Such conflict cause neurosis.
However, recent theories focused on biological factor. According to selectivemutism.org, amygdala, the almond-shaped area of the brain, cause children with selective mutism to be extremely anxious. This discovery is probably a fruit of brain science.
