This specialty examines, diagnoses, treats diseases affecting mental health including the brain, nervous system, substance abuse of drugs or chemicals and personality disturbances. Psychiatrists are medical doctors who specialize in treating mental illness using the biomedical approach to mental disorders, including psychotherapies. A psychiatrist specializes in the prevention, diagnosis, and treatment of mental, additive, and emotional disorders such as schizophrenia and other psychotic disorders, mood disorders, anxiety disorders, substance-related disorders, sexual and gender identity disorders, and adjustment disorders. A psychiatrist is able to understand the biologic, psychological, and social components of illness, and therefore is uniquely prepared to treat the whole person. A psychiatrist is qualified to order diagnostic laboratory tests and to prescribe medications, evaluate and treat psychological and interpersonal problems, and to intervene with families who are coping with stress, crises, and other problems in living.