Psychiatry is the branch of medicine focused on the diagnosis, treatment and prevention of mental, emotional and behavioral disorders.

A psychiatrist is a medical doctor (an M.D. or D.O.) who specializes in mental health, including substance use disorders. Psychiatrists are qualified to assess both the mental and physical aspects of psychological problems.

People seek psychiatric help for many reasons. The problems can be sudden, such as a panic attack, frightening hallucinations, thoughts of suicide, or hearing "voices." Or they may be more long-term, such as feelings of sadness, hopelessness, or anxiousness that never seem to lift or problems functioning, causing everyday life to feel distorted or out of control.

Some of the sub-specialities of psychiatry include:

• Management of addiction and rehabilitation
• Child and adolescent psychiatry
• Geriatric psychiatry concerning elderly patients
• Emergency psychiatry
• Military psychiatry
• Neuropsychiatry
• Sleep specialists

For most psychiatric disorders, there are no laboratory tests to confirm the condition. Instead, a patient undergoes a series of psychological tests, although biochemical tests are also performed to check the patient's physical health status.
Psychiatrists use several forms of treatment in managing mental health illness including psychotherapy, medications such as antipsychotics, mood stabilizers and antidepressants. Psychotherapy may include cognitive behavior therapy, family therapy or group counselling. Hospitalization may also be needed in severe cases.
Psychiatry is one of the oldest branches of medicine but the field has developed significantly since the advent of neuroscience. Standardized guidelines for diagnosis and treating mental health disorders are present in the various editions of the Diagnostic and Statistical Manual of Mental health disorders.