I was telling a friend of mine recently that I was going to be participating in another medical study, and I was rather surprised when her response was, "How does this benefit you?" I've been participating in studies for several years, and I can tell you, that's the first time I've ever received that particular response.
I won't lie. There are plenty of ways in which it does benefit me to participate in these studies, and that's part of why I do. I get paid — more for some studies than others — but because I don't get that money until the study is over (sometimes 4 or 6 months), that's not a major deciding factor. Many of the studies provide my insulin, needles, and test strips for duration of the study, which is a huge incentive for me, especially since my co-pays have gone up. Sometimes they provide gas cards (usually $20) for every visit you have to make to the doctor's office, which is nice considering the price of gas lately. Some study participants have to drive a long distance to get to the clinic, but I don't (and my car gets decent gas mileage), so those gas cards generally help to keep me in gas throughout the duration of the study.
I'd be lying if I said these weren't influential reasons why I do the studies, but they aren't the only reasons. I like being part of the process of new medications and devices coming out. I've gotten to experience continuous glucose monitors and new insulins this way. Usually these studies are a ways into the testing, too, so I don't have many concerns for my health and safety, and I can always back out of the study if that changes. And of course, there is always the satisfaction of knowing that I'm helping these new medications and devices become available to everyone. It's hardly my biggest reason for doing the studies, but it's still a good feeling.
So I'd say there's quite bit in it for me — but really, do I have to prove that in order for this to be considered a good thing?