Neuhouser and Dr. Ulrike “Riki” Peters were among more than 100 scientists from 116 institutions participating in the Coffee and Caffeine Genetics Consortium effort to conduct a genome-wide meta-analysis, the largest such study to date. The paper was published Tuesday in the journal Molecular Psychiatry.

Previous research led by primary study author Dr. Marilyn Cornelis, a research associate in the department of nutrition at the Harvard School of Public Health, had identified two loci, or genetic variants, found in people who drank the most coffee.

The new work quadruples the number of identified genetic variants linked to regular coffee use. In addition to two previously discovered variants, AHR and CYPIA2, the study discovered variants POR and ABCG2, which map to genes involved in caffeine metabolism, or the speed with which the body processes the stimulant drug.

Two other variants were discovered near genes BDNF and SLC6A4 that may influence the pleasurable or rewarding effects of caffeine, the study found. And two other variants, near genes GCKR and MLXIPL, which are involved in metabolism of glucose and lipids, had not previously been associated with the effects of coffee.

That’s all a technical way of saying the scientists think they’ve found new explanations for why so many people need a regular coffee fix. In the U.S. alone, more than 60 percent of adults consume coffee daily, according to the National Coffee Association.

“Lo and behold, it showed that the caffeine component is what’s driving our consumption,” said Cornelis, who has been working on the new paper since the last one was published in 2011.

It’s crucial to have a large enough sample to ensure that the findings are robust, said Cornelis. That’s why she relied on data from such a large number of researchers, including many who collected the coffee consumption information as part of other population-based studies of nutrition and disease.

In the case of Fred Hutch, Neuhouser and Peters provided data from the Women’s Health Initiative that included nutritional surveys with coffee consumption information from nearly 8,000 African-American coffee drinkers. Such data helped provide a perspective that was previously missing, Cornelis said.

More research is needed to learn the precise roles of the new genetic variants and what they might mean for individual response to coffee. Coffee has been linked to several health benefits, including a lower risk of Parkinson’s disease and Alzheimer’s disease, with possible effects on lower blood pressure and decreased rates of problems such as depression and stroke.

“Our findings may allow us to identify subgroups of people most likely to benefit from increasing or decreasing coffee consumption for optimal health,” Cornelis said.

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JoNel Aleccia is a staff writer at Fred Hutchinson Cancer Research Center. From 2008 to 2014, she was a national health reporter for NBC News and msnbc.com. Prior to that she was a reporter, editor and columnist for more than two decades at newspapers in the Northwest. Reach her at jaleccia@fredhutch.org.