It’s called “holiday heart” because it happens to binge drinkers who feel a flutter or irregular heartbeat after too many cocktails at parties. But a research review suggests it can happen after just one drink. Conventional wisdom, based on plenty of previous research, is that the occasional glass of wine or beer can be good for the heart, reducing the risk of heart disease and stroke as well as death from cardiovascular causes, lead study author Dr. Peter Kistler of the Baker IDI Heart and Diabetes Institute and the Alfred Hospital in Melbourne, Australia, told Reuters Health.

For the current study, however, researchers examined data collected on almost 900,000 people and found an eight percent risk increase for irregular heartbeat with each alcoholic drink consumed per day. “Alcohol is not universally ‘good’ for the heart,” Kistler said. “It is beneficial for the ‘plumbing’ or blood supply to the heart muscle, but for the ‘electrical’ part of the heart or the heartbeat it is not.” The study focused on what’s known as atrial fibrillation, a quivering or irregular heartbeat (arrhythmia) that can lead to blood clots, stroke, heart failure and other heart-related complications. Untreated, the condition doubles the risk of heart-related deaths and is linked to a five-fold increased risk for stroke, according to the American Heart Association.

The study doesn’t prove that an extra cocktail after dinner directly causes atrial fibrillation, the authors note. Still, they offer some theories about how spending too much time at the bar during holiday cocktail parties might be bad for the heartbeat. Drinking can damage heart cells directly and lead to small amounts of fibrous tissue within the heart causing an irregular heartbeat. The review found that people with atrial fibrillation who continue to drink are more likely to have ongoing irregular heartbeats even after a common surgery to repair the heart’s electrical system and fix the source of the flutter.