Diagnosis of depression involves a psychological/physical history and evaluation. According to the American Psychiatric Association, if a person experiences a loss of interest in the things they once enjoyed and are feeling sad, blue, or down in the dumps for at least two (2) weeks, and are experiencing at least five (5) of the other symptoms of depression, they may have major depression. If a person experiences euphoria, irritability, or a feeling of being "high" with four (4) other symptoms of mania for at least one (1) week, they may have bipolar disorder.

In addition to listing the symptoms, the doctor will also ask when the symptoms began, how long they have lasted, how severe they are, whether the individual has had them before, and if so, whether or not they were treated and what treatment was received, as well as whether or not other family members have had these symptoms.

Furthermore, a mental status examination will be done to determine if speech, thought patterns or memory have been affected. The physical examination will either diagnosis and/or rule out any medical conditions (such as thyroid disease, cancers or neurologic diseases) that could be causing the depression.