Psychiatrist:
A psychiatrist is a doctor with a medical degree (MD) who specializes in mental health. To become a psychiatrist, a physician must complete 4 years of medical school, plus a 1-year internship and a 3-year residency program in psychiatry. A psychiatrist is licensed to diagnose and treat mental, emotional and behavioral disorders, as well as to administer pharmaceutical medication (to prescribe drugs like anti-depressants, anti-anxiety medications, and more). While a psychologist can solely use psychological methods to help someone recovering from addiction, a psychiatrist can also prescribe medication. Sometimes psychologists and psychiatrists will collaborate to help a person with substance abuse issues -- for example, if a psychologist thinks medication may help their patient, they can refer them to a psychiatrist to be evaluated and possibly receive a medication. Psychiatrists are almost never involved in interventions; instead, they are actively involved in treatment.
MD:
A doctor of medicine (MD) degree is required to practice medicine in the U.S. It typically takes 4 years to earn an MD and doctors must also complete a 3-year residency to specialize in a particular field of medicine. A psychiatrist is an MD who specializes in mental health, including substance abuse and addiction. A licensed psychiatrist must have either obtained an MD or a DO (Doctor of Osteopathic Medicine) in order to diagnose and treat patients with mental, emotional and behavioral disorders. Doctors who hold MDs are almost never involved in staging interventions; instead, they are involved in treatment.