It probably depends on the meds and I am by no means an expert so take this with a pinch of salt, but I was on an antidepressant for 7 or 8 months at a relatively high dose but I found that after that point they didn't really work any more and my mental health started to get a lot worse again. I think for some people they can just stop working for no apparent reason, so I would recommend talking to your doctor about it to see if they think it would be worth changing the dose/meds