Now and then you’ll be looking at research and thinking “that’s interesting” .. or “we should do that” .. but perhaps there’s a nagging doubt in the back of your brain. I would encourage you to listen to that voice. And reflect. What isn’t this research telling me? What’s not being said?
Go and look at your PICO question. It’s quite likely to focus on the desired outcome (e.g. In patients undergoing moderate-emetogenicity chemotherapy, does adding olanzapine to standard antiemetics reduce nausea and vomiting?) rather than the possible disadvantages. I’m constantly encouraging people in training sessions to think about the negative consequences as well; a PICOO at the minimum. In the antiemetic example, how about “somnelence” or “extra-pyramidal side effects” or “reduced quality of life”?
When you’ve identified your nagging thoughts, remember too that trials aren’t great for side effect discovery , and that they are sometimes not reported fully . There should be a systematic search for adverse events alongside every systematic review assessing efficacy; but these are few and far between. And remember all the ways in which we sometimes don’t know or have uncertainties. 
Consider carefully when you’re reading research: “What’s not being said?”