Too often what started out as hitting up a bar for “a drink” with a friend turns into a night of bar hopping and heavy drinking, as more friends are called to join in on the fun. If you’ve ever been in this position, then you’ll remember what it’s like to go from zero to 100 over the course of the night. Or maybe you won’t, considering you got progressively drunker as the night wore on. Regardless of what you remember, there’s a really good chance that as more friends came through, your group got drunker more quickly — it’s been proven in a new study.

Published in the journal Addiction, the new study sheds light on young adult drinking behaviors and how they change for the worse with the influence of friends. It found that as more friends joined the group, the number of drinks a person had increased. But what’s more, the speed with which they drank also jumped, meaning people were not only drinking more but getting drunk even faster, too.

“This extends previous evidence that this increase is not due only to the higher number of friends present in the drinking situations,” the researchers wrote. “Other factors, such as decreasing self-control as levels of inebriation increase, or being increasingly involved in nightlife activities, such as dancing or playing drinking games, may be responsible for the acceleration in drinking pace.”  

The researchers, from the University of California, San Francisco and the Addiction Switzerland Research Institute, culled data from cell phone questionnaires distributed to 183 Swiss young adults with an average age of 23. The participants, about half of whom were women, were asked over the course of five weekends, every Thursday, Friday, and Saturday night from 8 p.m. to 12 a.m., to report how much alcohol they had consumed and the number of friends they were with. They answered these questions hourly on each night, Yahoo reported.

They found that the number of friends in a group tended to drop over the course of Thursday nights, while it remained stable through Friday nights, and increased from 8 p.m. to 10 p.m. on Saturday nights. Drinking pace accelerated on all nights but especially on Friday and Saturday nights, since the participants most likely didn’t have to work or go to school the next day.

The effect on drinking, the researchers found, was more pronounced on men than women, since they tended to have more friends appear — on average, men tended to have between 1.9 and 6.4 friends appear, while women had 1.8 to 5.7. “Men are… more likely to accept offered drinks, see drinking as a challenge, or perceive more permissive drinking norms than women,” the researchers wrote.

Studies have shown that young adults tend to drink more than any other age group, and that this behavior peaks around age 25. What’s more, a study from last year found that friends are more influential than others when it comes to downing shots, which gives credence to the accelerated drinking pace the researchers found.

Still, binge drinking, defined as four drinks for women and five for men within two hours, can be dangerous, and causes a range of health effects from unintentional injuries to alcohol poisoning and death. For this reason, the researchers said it’s important to develop prevention messages that alert young adults to the dangers they face when drinking excessively in groups.

Source: Thrul J, Kuntsche E. The impact of friends on young adults’ drinking over the course of the evening—an event-level analysis. Addiction. 2015.