I have found ssris really helpful over the past 10 years or so. I tend to end up taking them for 18 months or so, then very slowly taper off - am fine for around 9 months to a year then start to 'sink' again. If they are a placebo they are a really effective one for me.
I taper by titrating my dose against withdrawal effects which for me are a kind of 'spinning brain' feeling. I bite off a bit of a tablet to make it a bit smaller than yesterday's. If my head starts to spin, or I start to dip mentally, I nibble a bit more or take more the next night. Might sound loopy but it works for me. Usually take about 3 months to reduce to nothing.
I am aware of the arguments against them, but my "mixed anxiety and depression" comes out of nowhere, it is not situational (it is closely related to time of day and time of year) but if I don't treat it, I become exhausted with the effort of reminding myself that there isn't actually anything the matter, every 5 minutes, all day long.
ADs make my life so much easier, I am grateful they are straightforwardly available to me.
And the reason I taper is because I am aware there are possible adverse affects so my reasoning is that if I can manage without them some of the time it might be a good idea to do so. Not based on particular science, its just what I think. But after amount of time I am not surprised or particularly dismayed when I find its time to go back in them. Im just glad they're there.