We propose to use DNA probes to study patients having specific neurologic and psychiatric disorders, especially focusing on patients with early onset or extreme phenotypes such as childhood onset schizophrenia (COS), mental retardation (MR), attention deficit hyperactivity disorder (ADHD), atypical psychosis of childhood, (multi-dimensional impairment MDI), and bipolar affective disorder (BPAD). This study addresses the hypothesis that genetic risk factors contribute to these diverse phenotypes. Several complementary molecular genetic techniques are employed to identify chromosomal regions containing genes contributing to specific neurologic and psychiatric disorders. Patients will be selected for this study on the basis of the age of onset and severity of neurologic or psychiatric symptoms, familial genetic loading and family structure. Individuals participating in this protocol will be clinically evaluated through other NIMH or NIH clinical protocols, particularly through those of the Child Psychiatry Branch (reference protocol numbers 85-M-0115, 84-M-0050, 97-M-0126). Those subjects meeting inclusion criteria may undergo a screening that may include physical, neurologic or psychiatric examinations. As appropriate, this initial screen may be followed by more formal, structured instruments such as the Schedule for Affective Disorders (SADS), the revised Weschler Adult Intelligence Scale (WAIS-R), the Conner's revised parent and teacher ratings, and the Diagnostic Interview for Children and Adolescents (DICA- version IV) to confirm the clinical diagnosis at the discretion of the treating physician. Venipuncture and/or buccal swabs will be performed in order to obtain samples for DNA extraction or to establish a lymphoblast cell line to be used in genetic tests. Samples will also be collected from family members and controls for these studies.