Sure - I should have given some sources in my original comment. The order of my list of purported mechanisms is also not really ordered by significance. I think generally, more and more mechanisms of AD efficacy are discovered, and it can seem that the more we know, the less we know. Additionally of course, there are like 15 different classes of ADs, with hundreds of different compounds in total. What we know for sure I think is that the serotonin and also the monoamine hypotheses of depression are highly oversimplified and even internally contradictory, and many more targets and way more general biochemical mechanisms in the brain must be involved in depression.
- One source covering the 5-HT1A autoreceptor downregulation part in particular there is "Serotonin autoreceptor function and antidepressant drug action" (https://pubmed.ncbi.nlm.nih.gov/10890313/)
- I personally like the books "Antidepressants" by Leonard (that the previous paper is a chapter of) and "Anxiolytics" by Briley and Nutt. These discuss really a wealth of observed/purported mechanisms, also for example including the significance of late gene products.
- Wikipedia: Pharmacology of antidepressants (https://en.wikipedia.org/wiki/Pharmacology_of_antidepressant...) has great sources, especially on the anti-inflammatory and immunomodulative pathways, and introducing HPA axis modulation as another possible pathway.
