Demystifying Depression/Quantifying Depression
You will certainly have noticed the lack of scale in all the graphs herein shown. The truth is that research into depression has not yet reached the quantification stage. This is a pity, as much of the prejudice (especially in getting official recognition for the problem) could be avoided if there were tests which could estimate the seriousness of a depression. Which is not to say that such tests are not possible. In fact, in this section I intend to propose the means by which they could be developed.
At this point you might be thinking that blood pressure already provides a fine estimation. This is only partially true. Foremost, several factors other than stress levels have an effect on blood pressure. Furthermore, blood pressure is a static measure, unable to differentiate between the state of deep depression / low activity and the state of mild depression / high activity. This is an especially crucial distinction in the recovery phase of a depression. (Blood pressure is more reliable during the buildup phase towards a depression precisely because the activity variable tends to be always high, as people struggle to maintain a normal lifestyle).
My suggested test also relies on blood pressure, but adds a dynamic measure of that variable. In short, the idea is to build a graph showing how blood pressure progresses with time as the test subject performs a high-concentration activity. Figure 10 shows what one would be likely to expect from a healthy individual, a mildly depressed one, and one more deeply depressed.
Note that a depressed individual will typically not only have a higher blood pressure at rest, but more importantly, a steeper response curve. This could be the basis for developing an objective test of the seriousness of a depression. It would also be extremely valuable for tracking the progress of the illness.
The test activity is an open question. I would suggest a test which would require both high concentration and short-term memory. In my personal experience, I noticed that the simple game Concentration (the one where you are supposed to pick pairs of cards out of a large set of unturned cards) provokes an almost immediate response. It might be a good candidate for the test.
Obviously, there is a fair amount of noise which makes a precise measurement harder. How well the test subject slept the night before is one variable hard to control. Likewise for the degree to which they are enjoying the activity. Furthermore, other variables such as current medication and time of day would also interfere.
Another advantage of an objective test would be an estimation of how much time would be required until the test subject could be considered cured. I realise that there are several factors interfering with the progress of the illness, but given a large population of test subjects, one could compensate for factors such as age. It is only a matter of statistics, after all. In any case, a rough estimation is a lot better than no estimation at all.
At last, one small note of hope: there is research underway which uses imaging techniques such as fMRI to look directly into the brain and see the changes caused by depression. Unfortunately, it might take quite a long time before such research is put into practical use. The test I proposed is low-tech, potentially a lot cheaper, and could be developed immediately.