The common childhood anxiety disorder is Separation Anxiety (SA). As the name
implies, the anxiety of SA features fears of being away from people, including family
and sometimes friends, to whom the person with SA is close. 
Manifestations
of SA include difficulty sleeping alone, nightmares of harm to the person with
SA or people close to them, distress when parents or siblings do not come home
when expected, and difficulty leaving home and family to go to school or even the inability
to go to school unless there are siblings or close friends at school (in which
case the person with SA moves between friends and siblings, careful always to
have someone they are comfortable with close to them). It is thought that SA
often becomes GAD in adulthood. Think of the possibility of undiagnosed SA in
young adults who have trouble leaving home to live independently.
