This study represents a fusion of clinical, biological and behavioral research through an explanatory RCT of a parent-based treatment focused on modifying parental responses to child anxiety and distress as a mediator of treatment outcome, and on biological and behavioral markers as possible moderators of treatment outcome. The intervention evaluated in this study (Supportive Parenting for Anxious Childhood Emotions; SPACE) aims to systematically reduce FA through a series of concrete manualized steps. This study is an integrated explanatory RCT of SPACE with the following 3 specific aims: