Why irrational health scares happen

Have you ever gotten caught up in a public health scare that turned out not to have much of an impact? Most of us have, if we're being honest. In this 2011 video, Centers for Disease Control Director Thomas Friedan discusses the psychology behind irrational health scares. Take a look; it's short (about 90 seconds):

[PICTURE]

As Friedan points out, most people in more developed countries feel a great deal more anxiety about health threats that have very little chance of affecting them than they do about leading causes of death.

He uses the global health concerns associated with the March 2011 meltdown of the Fukushimi Daiichi reactor in Japan as an example, but it's easy to think of more recent examples. For instance, the 2014 West African Ebola virus outbreak received virtually nonstop coverage in the American media for much of the year even though just four US citizens contracted the disease in total. (In Brooklyn, NY, a bowling alley was even closed down for several days after one of these four citizens briefly stopped there.) It's hard to imagine such a panicked response to diseases that actually kill large numbers of people in the United States, such as heart failure and cancer.

Thanks to the infographics from this Business Insider post, you can easily visualize the relative lethality of a number of leading causes of death. The infographics below are based on numbers from the UK, but the leading causes of death are similar in the United States. (Ebola would fall into the broad "infections" category, but as the recent outbreak killed just one American, its individual bubble would be far too small to see on this chart.) If you live in a more developed nation, it's safe to say the the top causes of death should be of the most concern to you; the second chart is especially helpful because it outlines the risk factors that produce these mortality figures:

[PICTURE]

[PICTURE]

Note that the causes of death that tend to generate a great deal of fear — such as war, murder, mental health disorders, and suicide — kill proportionately small numbers of people, while banal conditions like heart disease, cancer, and respiratory disorders kill the most. It's also worth noticing the mundanity of many of the leading risk factors, like smoking, obesity, and poor diet. Illicit drug use, which is among the most feared health risks, comes in near the bottom of the rankings.

Why do people disproportionately fear such rare causes of death? Many factors play into this phenomenon, but two seem especially significant. The first has to do with the media, and specifically with the fact that news items about lurid subjects — such as violent crime, exotic diseases, or terrorism — tend to draw a lot more attention than other types of news. Since press outlets can't survive without an audience, they have a strong incentive to run stories on topics like these, especially when there's already a public furor around them. This effect can create a feedback loop in which coverage of a rare but frightening health threat increases the public's anxiety about that threat, which in turn encourages more coverage of it.

The second factor is inherent to our very brains. It's called the availability heuristic — the human tendency to estimate that examples which are easier to remember must be more important or more common. Since colorful causes of death are easy to recall, our brains tend to guess subconsciously that they must be especially common, even if we consciously know that they're rare. This effect can truly run haywire when it's combined with constant reminders of these rare forms of demise from the media.

This is a complex subject, and these two factors don't tell the whole story. Still, these charts are enough to suggest that it's worth reflecting carefully on the real risks before buying into the next widespread health