Earlier quoted context omitted.
A test can't be done in a lab on bloods but most of the time you can usually see the signs simply by observation and just talking to the person. I say the real problem is that it's hard to treat. When you see a close family member or friend suffering, you can't force them to go the doctors, where depression would certainly be diagnosed, and many often just don't go. The standard set of medication for depression usual…
And what I'm getting at is the fact that there SHOULD be a blood test. Or a biopsy. Or something more concrete. Is it not possible? I'd like scientific research to say that it is impossible.
I think the answer to both lies in the same area though, since the source of depression is not clear in the brain (I believe there was a study that shown SSRIs have an immediate effect on serotonin re-uptake yet takes a number of weeks to ease depression - implying serotonin doesn't play such a direct role as once believed).