Candy = Violence: Correlation, Causation and Association
Week after week, month after month, the health (and mental health) news headlines blare with the latest “link” between two things. Take, for instance, a few articles from just this past week we’ve published… Childhood cancer? Less likely to marry. Obese? Depression is more likely. Eat licorice while pregnant? Your child may have a smaller IQ. And my favorite from the past week? Eat candy as a child? You’re going to become a criminal.
Researchers seem content to draw these correlations, knowing full well their data shed little light on the actual problem. Instead, what they manage to do is to shed a whole lot of brain cells. Ours.
I’ll pick on the candy study because it’s low-lying fruit and it’s easy to make fun of. Let’s look at the data reported:
Researchers from Cardiff University in Wales looked at data on 17,415 children born in a single week during April 1970 in the United Kingdom. The data, from the British Cohort Study, included detailed health and lifestyle information on the children at several points during their lifetimes, including ages 5, 10 and throughout adulthood.
Thirty-five of those children went on to report at age 34 that they’d been convicted of a violent crime, the researchers found.
About 69 percent of those who reported having committed violent acts also reported eating candy daily at age 10, compared to 42 percent of those who did not have a violent criminal past, the study authors noted.
So let’s get these numbers straight, just so we have some perspective. Out of 17,415 children, only 35 of them were convicted of a violent crime? That’s astonishing, given that the UK has the highest violent crime rate in Europe. But what’s even more astonishing is that the candy-eating behavior of 17,380 children was not reported. What if 10,000 of those children also reported eating candy at age 10 daily? Wouldn’t that basically nullify the researchers’ findings?
Anyways back to what the researchers did report on… 24 of the 35 said they ate candy at age 10. Gee, I wonder what kind of association we’re now going to make, since things like gender and parenting style showed no significant differences between these two groups of children.
“There appears to be a link between childhood diet and adult violence, although the nature of the mechanism underlying this association needs further scrutiny,” said study author Simon Moore.
Really? Wow, indeed heady research there, Simon Moore. If you can’t say what the nature of the mechanism is underlying this association, I honestly have to wonder at the value of this research. What new information have you imparted to us?
Better yet, I wonder if there’s a more reasonable explanation that could explain this association.
“While it’s an interesting correlation, any scientist will tell you that a correlation never shows causation,” said Melinda Johnson, a spokeswoman for the American Dietetic Association.
“If there is any real link, my instinct is that the daily candy may be indicative of certain lifestyle factors that the researchers did not capture. For example, I do not see that the researchers were able to control for violence in the home. Perhaps children who end up violent as adults also tend to grow up in violent homes, and perhaps candy is used excessively as an ‘ease the pain’ tool.”
Another possibility is that a diet high in sweets is indicative of poor nutrition overall, which could have led to abnormal brain growth during a critical period of development, Johnson added.
Imagine that — something the researchers did not measure might adequately explain this association! Such as the immensely obvious theory that violent households might breed violent children (and candy is simply a byproduct of that relationship).
Researchers, unfortunately, are rewarded to publish, regardless of the merit of what they publish. You cannot be in an academic position for very long if you’re not constantly churning out rubbish like this.
Next time you see one of these sorry headlines or articles about an association between X and Y, know that one of the reasons you’re likely reading about the association on a site like ours or U.S. News & World Report or WebMD is because researchers need to keep their jobs and pay their bills.
As we continue to report on this research, keep a skeptical eye open and take such associations with a grain of salt. We will try and do our best to point out the obvious in such stories — correlation does not equal causation. The association we report on is of likely little value to anyone’s real understanding of the issue.
Now forgive me, as all of this talk about causation and correlation has made me hungry. For some candy.
Grohol, J. (2009). Candy = Violence: Correlation, Causation and Association. Psych Central. Retrieved on April 18, 2015, from http://psychcentral.com/blog/archives/2009/10/09/candy-violence-correlation-causation-and-association/