Tapered on and off 16 medications over the past 20 years, including just about every SSRI, SNRI, and TCA. One dose of Paxil (paroxetine) was enough to give me "mild" serotonin syndrome hyperactivity, plus disassociation like it was ketamine or a hypnotic. Mirtazapine worked well for me for about 8 years, far better than any other medication. Then it gradually stopped working so well. Tried Viibryd (vilazodone), which lead to eye and leg twitching. Also tried tapering off mirtazapine a few times in extended time periods, but I was right back in severe, crushing, depression.

I think the lack of scientific, evidence-based examination and treatment pushed by MDs/DOs, therapists, and psychiatrists is a big part of the problem. There is not much in the way of nosology or real personalized medicine going on to understand specific root cause(s). It's just throw random medications and therapy approaches "spaghetti" against a wall and hope something sticks.