Public health authorities are in a significant bind when it comes to persuasion. Encouraging people to adopt healthier lifestyles is key to better individual and social outcomes (from less disease to lower costs). Changing behaviour is, however, not easy as evidence from growing obesity rates to continued smoking . A further challenge emerges from the fact that science continues to evolve and, sometimes, challenge previously held beliefs.

Unfortunately, one of the consequences of social marketing campaigns is that while they struggle to convince some, they also create deeply held beliefs in many about the “righteousness” of various courses of action.

Just this week, Canadian women are being challenged to choose science when it comes to breast cancer screening (a good article about the issues is here). After years of promoting regular screenings and self-exams for all women, Canada (as well as other countries) has adopted a revised set of recommendations that significantly reduce the role of screening. For example, those women under 50 are not recommended to have mammograms anymore and the clinical and self-examinations are no longer recommended at all.

One of the reasons why the science in this case will not easily translate into change is that advocates of screening (doctors, survivors, other Canadians) have built up the case (rationally and emotionally) for screening to the point that many could probably resist arguments against screening (which new guidelines will just appear as).

The issue is important because the revised guidelines are not just about unnecessary tests — they are a response to analysis that indicates that the unnecessary screening has negative consequences for those who undergo them. And, in this, the argument bumps up against the dreaded “common sense.” How can a test produce a negative outcome?

When we move to probability and risk, the public is significantly challenged to understand how science works. And, when faced with this potential confusion may be less likely to accept the science by suggesting that it might be wrong.

The issue of breast cancer screening, is, however only one of many issues where science and health promotion are coming up against a skeptical or resistant public. Consider the following examples:

  1. PSA test for prostate cancer. The U.S. Preventive Services Task Force has recommended that healthy men no longer be tested because testing had no impact on mortality and was associated with significant negative effects resulting from false positive.
  2. The HPV vaccine which is supported by science and advocated by health promoters has run into significant resistance on the part of various groups. This reflects the significant resistance to vaccination in general, which at its worse has led some parents to intentionally expose their children to disease so that they build “natural” immunity.

Public opinion on these issues and the challenges of communicating advice based on science are illuminating. The question is why does science have such a hard time? Is it a function of the natural skepticism that is at the heart of all scientific inquiry? Or, it is all about our misguided “common sense”?