Psychiatry is the study of mental disease, which is a branch of medicine that deals with the diagnosis, treatment, and prevention of mental health disorders. It is a medical specialty that focuses on the evaluation, prevention, diagnosis, and treatment of mental, emotional, and behavioral disorders. Psychiatrists are medical doctors who specialize in mental health, including substance use disorders. They are trained to understand the biological, psychological, and social components of illness and are qualified to order diagnostic laboratory tests and to prescribe medications, as well as to evaluate and treat psychological and interpersonal problems.