Drugs, alcohol and lifestyle diseases: risk factors and evidence
Biology · Key Stage 3 · The School
Correlation is not automatically causation
A CORRELATION means two things tend to change together. As one goes up, so does the other — or as one goes up, the other goes down. This does not, by itself, prove that either one causes the other. A third factor could cause both. Or the link could just be chance, seen in a small set of data.
What makes a genuine risk factor
A RISK FACTOR is a lifestyle or environmental cause linked to a higher chance of a disease. Scientists trust a link as a real risk factor when two things are both true: the link shows up again and again, in many separate studies, AND there is a believable reason HOW the factor could cause the harm seen.
Known lifestyle risk factors
Smoking is strongly linked to lung cancer and heart disease. The reason is well understood: tar and other chemicals in smoke damage cells directly. Too much alcohol is linked to liver disease, since the liver has to process it and can be worn down over time. A diet high in fat, with little exercise, is linked to obesity, type 2 diabetes and heart disease, through several causes working together.
Smoking became firmly accepted as a cause of lung cancer for two reasons together, not one. First, the statistical link kept showing up, study after study. Second, scientists found HOW it happens: specific chemicals in tobacco smoke damage the DNA inside lung cells. That damage can be seen and measured directly in a lab, with no need for population statistics at all. A strong, repeated link PLUS a proven cause is what turns "these two things often go together" into "this causes that". A link with no known cause behind it should still be treated with real care, however strong it looks in the numbers alone.