The co-occurrence of two or more disorders in the same individual, and usually used in relation to psychiatric disorders, with reference to an initial diagnosis. Put another way, it is the presence of one or more disorders (or diseases) in addition to a primary disease or disorder, and the effect(s) of such additional disorders or diseases. Co-morbidity may affect the ability of individuals to function and survive. Distinguishing the primary disorders from the secondary disorders is a major issue in diagnosis, especially when concerned with developmental disorders.
See Apraxia, Attention deficit hyperactivity disorder (ADHD), Developmental disorders, Diagnosis (or diacrisis), Obsessive-compulsive disorder (OCD), Oppositional defiant disorder (ODD)