Friday, April 17, 2015

The many faces of the placebo response

This week, a study was published that claimed that the placebo response is mediated by genetics. Though I need to dig a little deeper and figure out exactly what this article is saying, I do think we need to take a step back and remember what can constitute a placebo response before we start talking about what this means for medical treatment and clinical trials.

In clinical trials, the placebo response can refer to a number of apparent responses to sham treatment:

  • The actual placebo response, i.e. a body’s physiological response to something perceived to be a treatment
  • Natural course of a disease, including fluctuations, adaptations
  • Investigator and/or subject bias on subjective instruments (hopefully mitigated by blinding/masking treatment arms in a study)
  • Regression to the mean (an apparent time-based relationship caused by one measurement that varies markedly from the average measurement)
  • … and many, many other sources

This week’s discovery does suggest that there is something physiological to the actual placebo response, and certainly genetics can influence this response. This may be useful in enriching clinical trials where a large placebo response is undesirable, e.g. by removing those subjects who are likely to response well to anything active or inert. After all, you don’t want an estimate of a treatment effect contaminated by a placebo response, nor do you want an impossibly high bar for showing an effect.

But we still need to remember the mundane sources of “placebo response” and lower those before we get too excited about genetic tests for clinical trials.

Tuesday, April 14, 2015

Helicopter parenting because your mind is "terrible at statistics" (or, rather, you are unaware of the denominator)

In Megan McArdle's Seven Reasons We Hate Free-Range Parenting - Bloomberg View:, she states that because of the news cycle, and because our minds are terrible at statistics, we think the world is a much less safe place than 30 years ago. It's true. We have more opportunity (because of the internet and cable news) to hear about tragedies and crime from far-away places. It's worse if such tragedy strikes closer to home. Thus, we tend to think the world is very unsafe. (And therefore are encouraged to become helicopter parents.) We are acutely aware of the numerator

What we do not hear, because it does not sell on cable news, is is the denominator. For all (very few) children abducted by strangers, for instance, we do not hear of the ones who successfully played at the park, or walked to the library, or went down to the field to play stickball (or I guess nerf softball because we shouldn't be throwing hard objects anymore) without getting abducted. This is because those stories do not sell.

I guess the second best is reporting on trends in parenting, and how they are driven by how bad we are at statistics (even statisticians).