Giving someone a "test" to find out if he or she might have depression is a very important tool. (Doctors call these tests "screenings.") They are a good starting point for helping someone who is depressed get the treatment they need.

Unfortunately, there is no single best test for determining if someone has depression. There are no laboratory tests available. (No blood test can reveal depression.) Instead, doctors have to rely on people providing honest answers to a series of questions. Some questions focus on the person's mood or state of mind. Others ask about possible symptoms of depression, such as changes in appetite, sleep pattern or energy level. Depending on the questionnaire, the person may answer yes or no to a series of question or choose a 0 to 3 range to represent the intensity of his or her experience. Someone who is depressed will have more intense responses, which are scored higher. As the score on the test increases, so does the chance that the person is depressed.

A great deal of work is dedicated to finding out whether screening tests are reliable and valid. These tests are used to measure how people respond to treatment, such as an antidepressant drug or psychotherapy.

The Beck Depression Inventory, first published in 1961, has been widely used and tested. It takes about 10 minutes to complete. Anyone with a fifth- or sixth-grade reading ability can take the test. Other tests include the Hamilton Psychiatric Rating Scale for Depression, the Zung Self Reported Depression Scale and the Center for Epidemiological Studies Depression Scale.

One of the largest screening programs is the National Depression Screening Day. It occurs every year in October, during Mental Health Awareness Week. Screening is done throughout the country. A large number of people participate; more than 100,000 people were screened in person in October 2004. At the screening session, you may be referred for a more complete evaluation if necessary.