Medical psychology is the application of psychological principles to the practice of medicine for both physical and mental disorders. The American Psychological Association (APA) defines medical psychology as "that branch of psychology that integrates somatic and psychotherapeutic modalities into the management of mental illness and emotional, cognitive, behavioral and substance use disorders". A medical psychologist does not automatically equate with a psychologist who has the authority to prescribe medication. Psychologists who hold prescriptive authority for specific psychiatric medications such as antidepressants and other pharmaceutical drugs must first obtain specific qualifications in Psychopharmacology.