you can't diagnose physiologically a low level of seratonin, can you? >> well, you actually can.patients have asked me about this, but i tell them i don't think you would want to do it, because we can do a spinal tap and we can get the spinal fluid level of seratonin and tell whether or not that's low. most people don't want to get a spinal tap to get treated for depression. >> i want to make one thing clear, and that these drugs are are prescribed for a physiological -- correct me if i'm wrong -- deficiency in the brain. is that correct? an imperfection? in the brain? if you had a perfectly functioning brain, you wouldn't need these drugs. >> who has a perfectly functioning brain? >> there are people. there may not be many of them, but there are people who are doing just fine. >> so that really, in itself, eliminates a great deal of the stigma, because you're talking about a physiological deficiency, correct? >> yes, and the good thing that's happened is we know much more about what's going wrong in the brains of people who are depressed and anxious now. >> so people who want to