June 19, 2023 — A new study challenges the widely held assumption that people who regularly drink to excess can “hold their liquor” better than people who don’t drink as much.

They may be able to function better than light drinkers when consuming their standard amount of liquor, but not so much when they consumed more than their usual amount, according to the study published in Alcohol: Clinical and Experimental Research.

“There’s a lot of thinking that when experienced drinkers (those with alcohol use disorder) consume alcohol, they are tolerant to its impairing effects,” Andrea King, PhD, professor of psychiatry and behavioral neuroscience at University of Chicago and the senior author of the study, said in a university news release. 

“We supported that a bit, but with a lot of nuances. When they drank alcohol in our study at a dose similar to their usual drinking pattern, we saw significant impairments on both the fine motor and cognitive tests that was even more impairment than a light drinker gets at the intoxicating dose.”

The research team tested 397 people who were classified as light drinkers who do not binge drink, heavy social drinkers who binge several times a month, and people with alcohol use disorder – also known as alcoholism — who binge frequently, about a third of the time. 

Participants received a drink containing alcohol, a stimulant, a sedative, or a placebo and consumed it over 15 minutes. The alcoholic level of the alcohol drink was based on body weight and was the equivalent to four or five drinks. 

Participants took a breathalyzer test and were given tests at intervals of 30, 60, 120, and 180 minutes. A motor skill test involved putting pegs in holes and a cognitive test asked them to match symbols on a piece of paper. Participants were also asked at the 30- and 180-minute marks to judge their impairment, from “not at all” to “extremely.”

The AUD and heavy drinkers said they were less impaired than the light drinkers. At 30 minutes, the heavy drinkers and the AUD drinkers did well with the cognitive test, while the light drinkers didn’t. But all three groups were equally impaired on the motor skills test at 30 minutes.

Additional tests were given to a subset of AUD drinkers in which they were given a beverage in line with their regular consumption, equal to seven or eight drinks. They showed more than double the amount of mental and motor impairment than after their standard intoxicating dose.