In medicine, a diagnosis is based on the history (talking with a patient and their families), a physical examination, and lab tests.

History

In adults, it is often possible to get by with only talking with the patient. This is never possible with children and adolescents. Children often will not say they are depressed. They are most likely to blame all their problems on school, friends, or family. Only by talking with the family can your doctor get an outside perspective. On the other hand, children are better reporters than their parents of their own feelings. The doctor needs to check for all sorts of other possible psychiatric disorders and other medical disorders, too.

Examination

In children and adolescents, this may mean a large variety of things, depending on the history. Besides doing parts of the physical and neurological exam, a careful assessment involves observing how the child behaves, does school work, and gets along with his or her family.

Lab Tests

This depends on the history, the exam and age of the child. Sometimes, no tests are necessary. Common things that end up being checked are thyroid tests, urine drug screens, tests for medical conditions that can mimic depression (infectious mono, for example), and other routine lab tests.

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