We don't have any good biological markers for depression at the moment. There's a strong possibility that there isn't any good biological proxy for the experien

We don't have any good biological markers for depression at the moment. There's a strong possibility that there isn't any good biological proxy for the experience of being depressed. The main problem with current diagnostic tests is that they give equal weight to a wide range of symptoms (sleeping too much, not eating enough, feeling hopeless about the future, wanting to kill yourself) that may have wildly different importance to the patient. A treatment can look good in clinical trials without necessarily having a big impact on a patient's quality of life. A biological test could be a retrograde step if it doesn't strongly correlate with the subjective hardships of depression.