Externalizing disorders (or externalising disorders) are mental disorders characterized by externalizing behaviors, maladaptive behaviors directed toward an individual's environment, which cause impairment or interference in life functioning. In contrast to individuals with internalizing disorders who internalize (keep inside) their maladaptive emotions and cognitions, such feelings and thoughts are externalized (manifested outside) in behavior in individuals with externalizing disorders. Externalizing disorders are often specifically referred to as disruptive behavior disorders (attention-deficit/hyperactivity disorder, oppositional defiant disorder, and conduct disorder) or conduct problems which occur in childhood. Externalizing disorders, however, are also manifested in adulthood. For example, alcohol- and substance-related disorders and antisocial personality disorder are adult externalizing disorders. Externalizing psychopathology is associated with antisocial behavior, which is different from and often confused for asociality.
Externalizing disorders often involve emotion dysregulation problems and impulsivity that are manifested as antisocial behavior and aggression in opposition to authority, societal norms, and often violate the rights of others. Some examples of externalizing disorder symptoms include, often losing one's temper, excessive verbal aggression, physical aggression to people and animals, destruction of property, theft, and deliberate fire setting. As with all DSM-5 mental disorders, an individual must have functional impairment in at least one domain (e.g., academic, occupational, social relationships, or family functioning) in order to meet diagnostic criteria for an externalizing disorder. Moreover, an individual's symptoms should be atypical for their cultural and environmental context and physical medical conditions should be ruled out before an externalizing disorder diagnosis is considered. Diagnoses must be made by qualified mental health professionals.