Psychiatrists are medical specialists who treat mental health problems. They generally only treat people who have severe or long-lasting problems.
A GP might refer you to a psychiatrist if you are not getting better quickly. Most psychiatrists work in private practice, but some are attached to hospitals.
Only in the most severe cases of depression, or where there is a danger a person might harm themselves, is a depressed person admitted to hospital. Most people with depression can be treated in the community.