Americans started drinking more as the Covid-19 pandemic got underway. They were stressed, isolated, uncertain — the world as they had known it had changed overnight.

Two years into the disaster, the trend had not abated, researchers reported on Monday.

The percentage of Americans who consumed alcohol, which had already risen from 2018 to 2020, inched up further in 2021 and 2022. And more people reported heavy or binge drinking,

“Early on in the pandemic, we were seeing an enormous surge of people coming in to the clinic and the hospital with alcohol-related problems,” said Dr. Brian P. Lee, a hepatologist at Keck Medicine of the University of Southern California and the principal investigator of the study, published in Annals of Internal Medicine.

“People assumed this was caused by acute stress, like what we saw with 9/11 and Katrina, and typically it goes back to normal after these stressful events are over,” he added. “But that’s not what we’re seeing.”

Alcohol can be addictive, “and we know that addiction doesn’t go away, even if the initial trigger that started it has gone away,” Dr. Lee said.

Rates of heavy drinking and of alcohol-related liver disease had been rising steadily for decades before the pandemic struck. But alcohol-related deaths surged in 2020, with one study reporting a 25 percent increase in a single year, said Christian Hendershot, director of clinical research at U.S.C.’s Institute for Addiction Science.