Do you like a cup of coffee or tea? Are you one of those people who can drink coffee all day and it will not affect your sleep? Or dose just one cup of coffee per day keep you awake at night?

Whichever category you fall into, it turns out it’s all in your DNA.

Researchers at the Harvard School of Public Health and Brigham and Women’s Hospital have conducted the first large-scale study to show how caffeine affects different people in different ways, and they have found that there are six genetic variants that play a role in the average person’s coffee consumption.

In the study, which is published in Molecular Psychiatry, over 120,000 people were polled about their coffee drinking habits. The researchers then analysed the DNA of all 120,00 individuals polled.

What they were able to prove are the six specific genetic components that influence the metabolic and neurological responses to caffeine.

Speaking to Science Daily, Daniel Chasman, associate professor at Brigham and Women’s Hospital and the study’s senior author, explained: “Like previous genetic analyses of smoking and alcohol consumption, this research serves as an example of how genetics can influence some types of habitual behaviour.”

The finding in this study will help researchers to better understand the potential health benefits and hazards of coffee as future studies are conducted.

Speaking to CNN, lead author Marilyn Cornelis of the Harvard School of Public Health explained: “Most (human) population studies of coffee and health assume everyone responds to a given amount of coffee in the same way.”

Mrs Cornelis went on to say “We know that isn’t true and we now have specific genetic variants that we can apply to our studies which will enable us to generate better results.”

Participants in the study who inherited just one or two of the genetic components identified were found to drink less coffee than those who inherited five or six.

So if you drink your coffee like most people drink water (regularly) now you know it may have something to do with your DNA.