A common misconception: If you get better after a treatment then the treatment must be effective

It’s an argument I’ve heard many times: Treatment X must be effective because it made me / my patients better. It’s a natural conclusion but it’s actually WRONG. Just because someone became better when they were taking a particular treatment does not mean that the treatment CAUSED them to get better. People recover from health problems for a range of different reasons. Here are some of the reasons people get better:

  1. Because of the actual treatment they were taking.
  2. Because they did something else unrelated to the actual treatment that made them better instead. For instance, sometimes people claim that they recovered from cancer due to taking an alternative therapy. On closer inspection it turns out that they took conventional treatment (such as surgery or chemotherapy) as well. It’s much more likely that the conventional treatment caused the improvement rather than the alternative one.
  3. They just recovered from the particular health problem / it ceased to be an issue. This is a LOT more common than most people think. Many health problems have a natural course where they are an issue for a finite period of time but subsequently cease to be a problem. Back pain is one example of something that often gets better on its own.

It’s only if a significant number of people fit into the first category that we can say that a treatment is effective. If someone goes for a particular treatment and their health improves, how do we know which of the above categories they fit into? In the normal course of events, we simply can’t know. That’s why we have clinical trials to assess treatment effectiveness. By comparing the treatment under test with other treatments (typically with the currently accepted most effective treatment) under controlled conditions it is possible to assess whether the treatment is effective or not. It is only if a treatment is shown to be effective under these controlled conditions that we can say that it’s actually an effective treatment.

For a more detailed review of why ineffective treatments can appear helpful please see the paper Why do ineffective treatments seem helpful? A brief review

In future, when someone tells you that a particular treatment “worked for them” or “worked for their patients” make sure that you ask whether there is any scientific evidence to back up this claim. If there isn’t any evidence then it’s impossible to say whether the treatment is effective and you should therefore assume that it isn’t.

Last updated 23/01/21