 Participation is voluntary. Families who choose to participate will be asked to make two visits to Childrens National. During their first visit, children and caregivers will be asked to complete self- and parent-report forms, as well as diagnostic interviews. Children will also be administered an abbreviated intelligence test. During their second visit, which is an optional component of the study, participants and one parent will stay overnight at Childrens National and children will undergo an overnight sleep polysomnographic evaluation. Between these visits, participants will wear wrist actigraphs for seven days. An actigraph is a small device that looks like a watch and measures sleep and wake periods. Families will be called daily during this week-long assessment and administered a brief phone-based assessment regarding childrens anxiety symptoms. Participants will receive some compensation for time and travel. 