Alcohol was probably the first mind-altering drug people came to rely on for a regular high, but exactly how it produces its buzz isn’t clear yet. Now a new study finds that the feel-good effects of spirits may be tied to the brain’s natural painkillers—the endogenous opioids.
The study was the first to image the brains of human drinkers and examine how and where alcohol affects endogenous opioid release. Researchers scanned the brains of 25 people they recruited from Craig’s List, 13 of whom were heavy social drinkers who imbibed between 10-20 drinks a week (10-16 for women, 14-20 for men). The rest drank fewer than seven alcoholic beverages weekly.
The authors found that in both groups, alcohol increased levels of endogenous opioids in the brain’s “pleasure center,” the nucleus accumbens. It also increased opioid activity in the orbitofrontal cortex (OFC), a higher brain region involved with reward, impulse control and with evaluating how desirable an experience, person or object is.
Compared to the light drinkers, however, the heavy drinkers reported feeling more intoxicated and a greater high— and the scientists figured out why. The heavy drinkers showed more opioid release in the OFC than the lighter drinkers.
The study “provides the first direct evidence of how alcohol makes people feel good,” lead author Jennifer Mitchell, assistant professor of neurology at UCSF, said in a statement. Not surprisingly, the better alcohol made people feel, the more likely they were to drink heavily in the feedback loop that is typical of some addictive behavior.
The research also offers insight into how naltrexone—one of only three drugs approved to treat alcoholism in the U.S.— may help alcoholics. Naltrexone (reVia, Depade or in long-acting injectable form, Vivitrol) prevents endogenous opioids from linking up with their receptors, essentially blocking alcohol’s ability to activate the reward centers of the brain and generate the alcohol high. Previous research has found that the drug is particularly helpful for people who have a mutation in an opioid receptor gene that results in greater activity in the pleasure center of the brain and is linked with increased risk for alcoholism.
Because the study did not include people with alcoholism, however, it does not address differences between drinkers who can control their consumption and those who cannot. Addiction tends to involve greater craving but less “high” from each drink or drug, so those who are addicted to alcohol may simply need more and more alcohol to become buzzed, since they may have become tolerant to the high that alcohol triggers, or their opioid system may be wired differently, such that they don’t feel the reward of drinking as intensely as others do. Mitchell’s study is a promising first step toward understanding alcohol abuse better — and hopefully finding more effective treatments.
The study was published in Science Translational Medicine.