Correlation does not imply Causation

One of the easiest fallacies to make is the Correlation-Causation Fallacy. This is a mistake where two factors are related (a Correlation) and it is incorrectly believed that one factor causes the other. I raise this because I saw an interesting article last week, and because the MMR-Causes-Autism claim is an example of the fallacy.
The article was about new research done on the link between oral hygiene and heart health. Researchers originally hypothesised that good oral hygiene had a protective effect. The full hypothesis was that bad oral hygiene resulted in dental plaque entering the bloodstream where it caused arterial buildup. The new research found that when other factors were controlled for, there wasn’t a causative link.
The correlation between good oral hygiene and heart health is because people who take good care of their general health are also more likely to take care of their dental health. Smoking, which has long been known to have a negative effect on heart health also negatively effects oral health. People who go to the dentist regularly are also more likely to go for checkups at the local GP. Those who brush and floss are more likely to exercise and eat right.
The MMR Vaccine is given at 18 months. Autism typically becomes noticeable at 18 months. Because of this correlation, some people believed that the MMR caused the Autism. Andrew Wakefield‘s tiny and fraudulent study was compelling because it looked plausible. As we now know, the MMR does not cause autism. The correlation is simply the period in which both occur.


About autismjungle

I am a Software Test Analyst. Shortly before I turned 21 I was officially diagnosed, although I had long suspected I was autistic. Welcome to my blog
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