Heavy drinking can alter DNA in ways that increase the desire for alcohol, new research suggests.
The findings may help explain why alcohol addiction is so powerful and hard to resist, say scientists.
The US team looked at two genes that play a role in the control of drinking behaviour.
One is PER2, which influences the body's biological clock, and the other POMC, which regulates stress responses.
The scientists then checked the DNA of groups of moderate and heavy drinkers, as well as binge drinkers.
They discovered that the two genes had undergone "epigenetic" changes in both heavy and binge drinkers, but not moderate drinkers.
Rutgers University senior researcher Professor Dipak Sarkar said the DNA changes could lead to more cravings in heavy drinkers.
"We found that people who drink heavily may be changing their DNA in a way that makes them crave alcohol even more," he said.
"This may help explain why alcoholism is such a powerful addiction, and may one day contribute to new ways to treat alcoholism or help prevent at-risk people from becoming addicted."
The findings, published in the journal Alcoholism: Clinical & Experimental Research, were backed by experiments involving real life responses to alcohol.
Participants were shown an array of neutral, stress-related or alcohol-related images as well as containers of beer, which they were invited to taste.
Their motivation to drink was then evaluated.
The results suggested that the genetic changes observed earlier caused binge and heavy drinkers to be more drawn to alcohol.
In the background to their research, the scientists cited a World Health Organisation report which said that in 2016 more than three million people died as a result of alcohol abuse.
More than three-quarters of these alcohol-related deaths were among men.
