Drinking alcohol makes people feel better because it produces the same chemicals in the brain as exercising and laughing, a study has proved for the first time.
Alcohol is addictive because it releases endorphins, which are the body's way of making us feel pleasure and reward, the researchers showed.
The stress and pain-relieving proteins are naturally released in the brain and other tissues, producing similar effects to opiates such as morphine.
Brain scans conducted to show the immediate effects of alcohol on the brain provided the first direct evidence to support scientists' belief that it triggers the release of endorphins.
The discovery of the particular brain regions where the endorphin release takes place could help scientists develop new treatments to help people overcome alcohol addiction.
Dr Jennifer Mitchell of the University of California, San Francisco, who led the study, said: "This is something that we've speculated about for 30 years, based on animal studies, but haven't observed in humans until now.
"It provides the first direct evidence of how alcohol makes people feel good."
Researchers conducted positron emission tomography (PET) scans on the brains of 13 heavy drinkers and 12 non-drinkers immediately after they drank alcohol.
Their findings, published in the 'Science Translational Medicine' journal, showed that alcohol caused endorphins to be released in the nucleus accumbens and orbitofrontal cortex brain regions.
Meanwhile, internet addiction disrupts nerve wiring in the brains of teenagers, a study has found. Similar effects have been seen in the brains of people addicted to alcohol, cocaine and cannabis.
The discovery shows that being hooked on a behaviour can be just as physically damaging as addiction to drugs, scientists believe. The study was carried out by the Chinese Academy of Sciences in Wuhan. (©Daily Telegraph, London)