Asking for trouble.

According to the New York Times, the US Preventive Services Taskforce is about to recommend against routine prostate-cancer screening, based on the results of randomized trials that didn’t show any decrease in overall deaths.   We’ll come back and discuss the report when it actually appears, but this recommendation is going to be profoundly unpopular with certain groups, most dramatically with men who have had prostate cancers detected and removed.

One of the biggest problems in recommending against an existing screening method or treatment is all the complaints from people who think they have personal experience of its effectiveness (most of whom, I can safely predict, won’t actually bother reading the report before denouncing it).  The idea that an individual can know that a treatment works, based just on personal experience, is a very powerful cognitive illusion.  It can’t possibly be true — medical science would be so much simpler if it were — but the perception is unavoidable.   For example, I had mild `walking’ pneumonia a few years ago, and got sicker over a period of weeks, then got treated, and suddenly started to feel better.  It certainly felt as if the treatment worked, but when I later talked to some experts I found out that there is very little reason to believe that antibiotics are helpful for the sort of illness I had, and suddenly starting to feel better is exactly what happens when your body finally gets on top of an infection.  Even so, if you hooked me up to a polygraph you would find I still believe the treatment worked for me.

Cognitive illusions are much like optical illusions: these lines don’t look straight, and you can’t learn to see them as straight, no matter how much optics you study. You just have to decide who you are going to believe — the evidence, or your own lying eyes?