Genes may be implicated in dysfunction in the amygdala, the core structure for the acquisition of fear.

There is substantial evidence to suggest that genes play a role in the dysfunction of the amygdala, particularly in the acquisition and processing of fear. For example, studies on twins have shown that genetic factors are responsible for up to 50% of the variation in amygdala size and activity, and studies on mice have identified specific genes that are necessary for the normal development and function of the amygdala.