A new study shows that people who carry a particular version of two specific genes are more likely to consume caffeine.
Harvard researchers analyzed the genes of more than 47,000 middle-aged Americans.
Participants with the "high-consumption" version of the gene drank about 40 milligrams more caffeine per day than people with the "low-consumption" gene.
Scientists knew an inherited trait existed for caffeine consumption, but this is the first time they've found the major genes involved.
The study appears in PLoS Genetics, a journal published by the Public Library of Science.