During the COVID-19 pandemic, people in many countries on earth drank more than ever to cope with the negative psychological effects of everything from bereavement to social isolation to financial distress. While drinking may be more socially acceptable than smoking or doing drugs, alcohol is nevertheless a confirmed carcinogen, meaning that it can contribute to the development or progression of several cancers.

A new study published in the journal Lancet Oncology quantifies that global cancer burden. Researchers with the World Health Organization’s International Agency for Research on Cancer (IARC) estimated that at least 741,300 of the roughly 19.3 million new global cancer diagnoses reported in 2020—4%—can be attributed to alcohol consumption.

While excessive drinking was responsible for most of the cancer incidence, even moderate drinking, that is, consuming one or two alcoholic beverages a day, was statistically linked to 103,000 new cancer diagnoses—about 14% of the total.

However, fewer than one in three U.S. citizens are aware that alcohol is a cancer risk factor, IARC researcher and study author Harriet Rumgay told NPR. "That’s similar in other high-income countries, and it’s probably even lower in other parts of the world,” Rumgay said.

In the study, the majority of the new alcohol-associated cancer cases occurred in men, though more than 100,000 women were affected as well. Overall, those cancers included mouth cancer, liver cancer, colorectal cancer, laryngeal cancer and esophageal cancer; for women, however, alcohol also contributed significantly to breast cancer.

In addition to damaging existing cells, drinking can elevate cancer risk by decreasing absorption of cancer-protective nutrients and facilitating the production of hormones that promote cell division, such as estrogen, according to NPR.

“Increased estrogen levels happen with increased alcohol consumption, and that’s probably a part of the link of why breast cancer is more prevalent in people that drink alcohol," Rodney Young, the chairman of the department of family and community medicine at the Texas Tech University Health Sciences Center School of Medicine, told ABC 7

Rumgay and colleagues chose not to include cancers caused by previous rather than current drinking or cancers that have only recently been associated with alcohol consumption, including stomach cancer and pancreatic cancer, in their estimate, according to NPR. Therefore, they characterize the figure as conservative. “When we did the analysis and included former drinking, pancreatic [cancers] and stomach cancers, the numbers increased to 925,000 alcohol-related cancers,” Rumgay told NPR. 

The greatest incidence of new alcohol-associated cancer diagnoses occurred in Moldova and Romania, Rumgay said. However, drinking trends seem to be changing worldwide. In those Eastern European countries, new taxation policies have reduced alcohol sales, potentially forecasting a decrease in annual cancer diagnoses. In China, India, Vietnam and many sub-Saharan African countries, by contrast, drinking rates are on the rise. Experts say those nations will likely see a corresponding spike in cancer rates in the coming years.

For more on how pandemic drinking has affected health, read “COVID-19 Worsens Mental Health, Sparks Overdoses” and “Pandemic-Fueled Alcohol Abuse Creates Wave of Hospitalizations for Liver Disease.”

For more on alcohol and cancer in the United States, see “Alcohol Consumption Linked to Cancer Incidence and Mortality in All States.”