I've known for a while that "studies" can't be trusted, nor can the media's reports about said studies because they fiddle with the statistics (an example I read a while back: "Obesity causes a 50% increase in kidney cancer!!!"--they failed to clearly point out, however, that any random person's chance of kidney cancer is well below 1%, so a 50% increase still doesn't bring an obese person's chance of kidney cancer to 1%; that seems a lot less worrisome, right?).
This article is on an important number that comes out of drug studies that isn't published in obvious places, but is a number your doctor should be able to pull from his drug books: Number Needed to Treat. In the article's example of a cholesterol med, of 100 people with high cholesterol, only 2 managed to avoid a heart attack by taking the med. A few had heart attacks anyways and the vast majority--over 90%--didn't have a heart attack nor were any less likely to have one due to the medicine. The NNT for this drug was 50--out of every 50 people who take it, one derives some benefit.
I think this NNT number is something everyone should be asking about when they are taking preventative medicines (and even some non-preventative medicines). For instance, we were just discussing last week the fact that someone's cholesterol medicine was making her IBS worse; at the very least, her IBS got better when she went off it. If the NNT is 50 or higher--if only 1 person in 50 or more derives any benefit--and it is suspected of causing her IBS, then it certainly doesn't seem worth it, does it?
I think this number could be very important for a lot of people who are unsure if they want to take a medicine and who feel guilty about dropping medicines which make their IBS worse. If the chances of a benefit are pretty low and the chances of side affects pretty high (especially IBS side effects), then the choice about whether to take it or not seems pretty clear. Just ask your doctor about the NNT for any meds he is putting you on (note the article also mentions antibiotics and their effectiveness against some problems--wouldn't you like to know the chances of getting better before you take antibiotics and potentially screw up your guts?). If you don't feel that the odds for a benefit outweigh the potential or known side effects, or even outweigh the cost, just tell your doctor you don't want to take them. No one is forced to take the meds a doctor prescribes, but you should let him know that you're not taking them and why so he at least has an accurate picture of your health and your drugs.