Correlation or causation? In research, bet on the former

If trying to assess the risks and benefits of various foods, behavior and whatnot leaves you wanting to gorge on Oreos until you no longer care, small wonder. News coverage of medical and science studies, especially the headlines, often takes a few liberties when it comes to correlation and causation.

To be fair, most headlines can only hold so many words. (Note to headline writers: When in doubt, go with the all-purpose and deliberately vague "link." It's hard to argue with "link.")

So think it through. Did that study actually conclude that chocolate reduces stroke risk? (Something you're going to be hearing a lot about as we approach Buy Chocolate Because That's What You're Supposed to Do Day.) Or did it conclude that people who regularly eat chocolate are less likely to die of stroke?

It's hard to prove the former; and many, many things could affect the latter. Perhaps people who allow themselves to have a bit of dietary pleasure are simply less strung out and have fewer stroke risk factors to begin with. 

Here's David Katz of Yale University's Prevention Research Center weighing in on that topic (and a timely review of chocolate-related research) in this ABC News story.

And here's an explainer of cause and correlation from STATS at George Mason University. It states:

"An action or occurrence can cause another (such as smoking causes lung cancer), or it can correlate with another (such as smoking is correlated with alcoholism). If one action causes another, then they are most certainly correlated. But just because two things occur together does not mean that one caused the other, even if it seems to make sense."

And here are one professor's "you goofed" examples from the mainstream media. Fair enough. We each have our own "correlative-confused-with-causative" favorites.

-- Tami Dennis

Photo credit: Bob Chamberlin / Los Angeles Times

Comments

[David]

This is why I wish that all science reporters had at least introductory graduate statistics and research methods training. Remember and appreciate that you are the gatekeepers. Extremely few people will actually read through our published papers while many will read even the smallest blurb from a source like the LA Times. Please continue to do your due diligence on this issue.......also, something that very much bothers me, science writers (being journalists by training for the most part) tend to want to offer "both sides" of the story when in reality, science often has a correct side and an incorrect side. There is no reason to give lip service to the "other side" when there is no scientific support. I would think that enacting these two suggestions would prevent a lot of public confusion (see vaccinations and autism).

[Hair Loss Shampoo]

It seems like every scorching health headline regarding the benefit/risk of substance X is always refuted 6 months later only to be reversed again 6 months after that. The complexity of the human body and the chemical reactions and bifactors that occur every second, make it almost impossible to accurately claim "substance X" solely is responsible for "health problem Y".

[MJ]

Science rarely "proves" or decides on causative factors. Science is VERY good at disproving and correlating, however.

This is an essential point that many people in the public are unaware of... good article.