A little. There's some studies I won't do just based on word of mouth experiences of other participants. I won't do any studies where the medication is treating Alzheimer's, and I'm a bit wary of those treating Parkinson's and schizophrenia. Had a roommate who did a study at Celerion in Arizona who did an Alzheimer's where most of the participants in her study, including her, became pretty sick. The med lowered their white blood cells, and they caught something. This was several years ago. In another instance, a woman in her 60s told me that the Alzheimer's med she took caused her to almost forget where she lived.
Oh, yeah. I absolutely won't do anything that has lumbar punctures where they take some of your spinal fluid. Those are rare to come by though.