Behavior problems that affect how a child relates to his or her environment.

In contrast to internalizing disorders—the other broad category of childhood behavior disorders—externalizing disorders are manifested in children's outward behavior rather than (or in addition to) their internal thoughts and feelings. These disorders include problems of control, such as conduct disorder, and problems of inattention and impulsivity, such as attention deficit/hyperactivity disorder (ADHD). Internalizing disorders include depression and various types of anxiety, such as separation anxiety disorder and generalized anxiety disorder. Some disorders, such as autism, are not categorized as either internalizing or externalizing disorders.