Psychiatry includes many aspects of understanding and treating the problems of the mind, brain, and personality. Although psychiatry includes Psychology, it is not the same. Only doctors who have graduated from a medical school, M.D. or D.O., may prescribe medications and are called "doctors." Medical doctors with specialized training (residency) are called psychiatrists. (Some nurse practitioners may also prescribe medications, but they are not called "doctor" and they are under a medical doctor's supervision.)
While any medical doctor may prescribe psychiatric medications, only psychiatrists have had specialized training to do so. An internist, family doctor, or pediatrician will often treat the more common mental symptoms and disorders. The more complicated a behavior problem, mental symptom, or mental illness is or becomes, the more likely that a specialist should be consulted.
Psychiatry also includes many different areas of additional training called subspecialties: like child & adolescent, addiction, geriatric, and forensic. If addictions are the issue, you may want to see someone with additional special training in addictions. If your child or adolescent has behavior problems or mental struggles, you might want to see a child and adolescent psychiatrist. Likewise, if you are 65 years old or older, you will want to see a geriatric psychiatrist.