One of the stronger hypotheses for depression is that of cytokines. This is a group of substances that have a number of functions in the body, but at the moment we are interested in those that have pro-inflammatory effects. Colloquially speaking, in some patients depression may be caused by chronic inflammation in the brain.
Approximation of the whole issue is impossible on a small website, aimed at people without medical education. If you are interested, I would refer you to a solid study that cites over 400 other scientific papers and draws conclusions based on those papers. Yes, the science is that complicated. You have to collect over 400 different scientific papers, each requiring hours or days of work to fully understand, only then can a picture emerge.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3741070/
Instead of trying to do the impossible, I will focus on what is really important for the “common man”, on methods of lowering the level of pro-inflammatory cytokines, which in some patients should bring a very big improvement. The authors of the above study, as befits doctors, are not trying to find the cause of the increased levels, but are looking for patentable drugs to lower them temporarily, preferably ones that have to be taken for life.
In the chapter on supplements, I discussed boron – who knows, maybe this is where the secret to the success of the therapy that the participants in that forum came up with lies? Supplementation with boron clearly reduced levels of pro-inflammatory cytokines:
https://www.ncbi.nlm.nih.gov/pubmed/21129941
Of the other things that can effectively lower levels, the most commonly mentioned are:
Mediterranean and vegetarian diets
magnesium
chromium
omega 3
histidine and beta alanine
garlic
meditation
vitamin B12
spirulina
There is no way to test cytokine levels in a laboratory. Yes, there are tests, but they are quite expensive and not very reliable. Their concentration in blood changes not even from day to day but from hour to hour. To assess their impact on disease in the population, you need to test hundreds of people and draw an average. In order to assess the influence on one’s own health, one needs to perform several dozen of tests and from them draw an average concentration for oneself.
Since elevated concentrations of cytokines are detrimental not only to depression, but also to overall health, it is worth trying to lower them using the methods mentioned above. And no, it doesn’t work as simply as the charlatans try to make you believe, there is no single supplement that “eliminates inflammation”, and certainly not vitamin C.