Americans are in full holiday mode, reveling in the eating, drinking, shopping, traveling, partying and family visiting that have come to define this most wonderful time of the year.

But at Cooper University Hospital (search) in Camden, N.J., Thanksgiving launched a slightly different season: Through the New Year, doctors there will see an uptick in patients suffering from atrial fibrillation — an irregular heartbeat — caused by drinking excessive amounts of alcohol.

Dr. Vijay Verma, a cardiac fellow at Cooper, said he and his colleagues have termed the condition "holiday heart syndrome," because patients come in complaining of chest pain and palpitations the morning after a night of binge drinking.

Food, family, friends, fun. Too much of a good thing can be a bad thing when the frenzy of festivities wreaks havoc on your physical and mental health.

It’s not just the physical risks posed by overeating and over-imbibing. Bills tend to bloat along with bellies at this time of year, and family tensions swell along with waistlines. For many, the stress, exhaustion and anxiety brought on by the holidays not only take their psychological toll, but actually cause people to sooth that stress by smoking, drinking alcohol and overeating even more than usual.

Doctors say that a person in good health can weather some holiday indulgence with little worry or guilt. But for people with pre-existing medical problems, the holidays often lead to serious health crises.

Holiday Health Hazards

John DeCastro, Ph.D., an expert on eating behaviors who chairs the psychology department at the University of Texas at El Paso (search), said human beings are biologically programmed to eat more during the autumn months; it was our ancestors’ way of storing up fat for the winter. Humans have also been culturally programmed over the centuries to eat more when they are sharing a meal with others. A few extra calories at this time of year shouldn’t sabotage someone’s otherwise good health.

"You really have to put into perspective that it doesn't matter what you do on Thanksgiving Day, it matters what you do throughout the year," DeCastro said. After all, it’s the excess that makes it a holiday. "Turn a wonderful event with family and friends into a guilt-ridden event? No, thank you," he said.

However, people with existing health issues — heart disease, diabetes, high blood pressure, obesity — can’t afford such indulgences. For them, such excess can be downright perilous.

For example, the "holiday heart syndrome" Verma described usually subsides after the alcohol passes through the system — unless the patient is already suffering from heart disease. Additionally, Verma said, people who must observe special diets or take medication tend to go off them in the midst of holiday hustle.

These lapses can lead to heart attacks and be fatal, Verma said.

"We do tend to see more people on the holiday itself or the day after," Verma said. "More patients also have heart attacks around the holidays," he added.

In a 1999 study of Los Angeles County, Dr. Robert Kloner of Good Samaritan Hospital (search) in Los Angeles found that heart attack rates spiked by 33 percent in December and January. Deaths from heart disease also peaked, up from 1,400 in the spring and summer months to 1,800 in December and January.

What’s more, a recent Harris Interactive survey of 1,017 adults with high blood pressure found that people with hypertension tend to eat, drink and smoke more than usual between Thanksgiving and New Year’s Day. The survey, commissioned by Biovail Pharmaceuticals Inc., found that 62 percent of adults with hypertension eat more than usual; 37 percent gain weight; and 29 percent exercise less or quit exercising altogether.

Dr. Dorothy Cantor, a Westfield, N.J.-based psychologist, said those already at risk often look to the holidays as a time to escape their health problems.

"There’s a permissiveness at these occasions," Cantor said. "You think you’re giving yourself a gift, but you have to ask yourself is the real gift indulging or taking care of yourself."

It’s not a very merry time of year for the obese and overweight, either. While an average-weight person is likely to gain about one pound during the holidays, a recent study by the National Center for Health Statistics found that people who are overweight or obese are likely to gain an average of five pounds during the holidays — weight they never lose, but add to year to year.

Verma’s advice for the holidays is simple, "Take it easy and enjoy things in moderation, but be sure to keep compliant with diet restrictions and medications."

The Stress Factor

The exact role that stress plays in health can be difficult to quantify, Verma said, but its effect is undeniable. The Harris poll found that 48 percent of the hypertension patients surveyed also experience heightened stress levels during the holidays. For some patients, stress itself can exacerbate underlying heart conditions. For others, it’s the "coping" behavior — increased smoking or drinking — that causes the problems.

In diabetics, stress physically manifests itself by triggering an increase in hormones that spikes blood sugar levels and causes fatigue and extreme thirst, doctors say.

Not So Merry

Contrary to popular belief, neither suicide nor depression increases during the holidays. Mental health experts are eager to set the record straight. According to the National Center for Health Statistics, suicides actually drop during the winter months; both depression and suicide peak during the spring and summer. Likewise, a widely reported study by the Annenberg Public Policy Center last year labeled reports of holiday-related suicide a "media myth."

Still, the "holiday blues" is a real condition for many, particularly those with troubled family relationships, histories of alcoholism or drug abuse, pre-existing emotional or mental health issues, or those dealing with personal problems like divorce or unemployment.

"If you already have emotional issues, you’d better watch yourself around the holidays," Cantor advised.

Some mental health experts advise foregoing the year-end reflection on the past. Look to the future, they say. Others warn about falling victim to having unrealistic expectations for the holidays.

"There’s an assumption that we’ll all be jolly, but there are other things going on like illness, work, or financial troubles," said Cantor. "Step back from it all and ask yourself what you want, find your voice and take control. If you don’t restore yourself, how can you help those around you?"