Caffeine craving or addiction stems from a person’s genes, a new study has found out.

According to LiveScience.com, the study identified two genes, namely CYP1A2 and AHR, involved in the breakdown of caffeine in the liver that are associated with the amount of caffeine people consume.

Findings suggest that the reason some people drink more caffeine than others is because the heavy drinkers are better able to tolerate it.

“[The] liver, more than [the] brain, determines daily caffeine intake,” said study researcher Neil Caporaso of the National Cancer Institute. “You might think, I drink caffeine to feel good, or not to feel bad, but that, in turn, is established by how fast your liver breaks down the caffeine,” Caporaso said. “If your liver breaks it down very rapidly, then likely you drink more.”

More than 90 percent of U.S. adults consume caffeine, whose effects can either be good or bad, such as resulting to cognitive impairment, insomnia, and hallucinations.

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