Excessive consumption of alcohol can change DNA in ways that increase the desire for alcohol, new research shows.
These findings can explain why alcohol addiction is so strong and hard to resist, scientists say.
The American team watched two genes playing a role in controlling drinking behavior.
One is PER2, which affects the biological body clock, and the other at POMC, which regulates stress reactions.
Scientists then checked the DNA group of moderate and heavy alcoholics as well as drunk.
They found that these two genes experienced "epigenetic" changes in both the harder and the drunkards, but not the moderate drinkers.
Senior Researcher at Rutgers University professor Dipak Sarkar said changes to DNA could lead to more craving for heavy alcoholics.
"We've found that people who drink heavily may change their DNA in a way that is even more desperate for alcohol," he said.
"This can help explain why alcoholism is such a powerful addict, and one day it can contribute to new ways of treating alcoholism or helping prevent dangerous people from becoming addicts."
Findings, published in the journal Alcoholism: Clinical & Experimental Research, have been substantiated by experiments involving real-life alcohol reactions.
Participants are shown a series of neutral images of stress or alcohol, as well as beer containers that are called for taste.
Their motivation for drinking was then evaluated.
The results have shown that the previously observed genetic changes have caused alcohol to be more attracted to alcohol.
In the background of their research, scientists reported the World Health Organization report that in 2016 more than three million people died of alcohol abuse.
More than three-quarters of these deaths associated with alcohol were among men.