What test do you thinks is the best test for depression?

None specific: Depression is an emotion or "feeling" and to me it suggests underlying poor health in the body/brain communication system.There may therefore be abnormal lab studies, e.g. Markers for inflammation because that is initiated by the brain. The brain and body always work together so the brain affects the body and vice versa.

Diagnostic tests: Most "tests" like the Dexamethasone suppression test have been for research use. Some researchers are also working on a blood test for biomarkers of depression, but it isn't ready for prime time. There are also various questionnaires, such as the ces-d: http://tinyurl.Com/949ca5o at present, our best diagnostic tool is a focused interview with the patient plus ruling out other medical issues.

DEPRESSION: Get an evaluation from a psychiatrist to help identify what depression means to you and whatever else may be bothering you. Consider recommendations for medication if any are given. Get a referral for a reputable psychotherapist to speak with. Meds and therapy combined are most optimal; no just one or the other.