Your head is pounding, your mouth feels like cotton, and the nausea is crippling. The light streaming through the window and the buzzing of your alarm clock make your headache even worse. You hide under the covers wanting to sleep, but you can’t.
Nearly anyone who’s ever had a night of moderate to heavy drinking knows firsthand the misery of a hangover. In fact, hangovers are so common that 35 to 50 percent of adults who drink alcohol experience one at least once a year.
A national survey found that more than 9 percent of U.S. workers went into work with a hangover at some point in the previous year. And a Dutch study found that university students in the Netherlands tend to suffer from a hangover nearly three days out of every month — which amounts to about one “lost” month every year.
As widespread as hangovers are, scientists aren’t precisely sure what causes them. Their best guess is that multiple factors — including dehydration, inflammation and byproducts of the way the body processes alcohol — contribute to the unpleasant experience of being hungover.
Hangovers don’t occur until after you’ve stopped drinking and your blood alcohol levels are falling. Symptoms peak, or reach their worst point, when blood alcohol content returns to zero.
The length of time it takes to reach a blood alcohol level of zero can vary widely depending on your biological sex, your weight and how many drinks you’ve consumed.
It typically takes a 140-pound woman who consumed five drinks more than 10 hours to reach a blood alcohol level of zero. By comparison, a 180-pound man who consumed five drinks would have no alcohol in his blood after about six hours.
Most people who’ve drunk too much first notice hangover symptoms when they wake up. Common hangover signs and symptoms include:
Rapid heart rate and high blood pressure are also common physical symptoms of a hangover, though people may not notice these changes. Hangovers can also cause memory problems, coordination difficulties and reduced reaction time.
People with an alcohol addiction might not experience hangovers because their body has developed a tolerance to alcohol.
Scientists have many theories about what causes hangovers, but they have not settled on a single, definitive explanation for the phenomenon.
One school of thought considers hangovers a mild form of alcohol withdrawal. In fact, many similarities exist between the symptoms of a hangover and alcohol withdrawal symptoms.
Like a hangover, alcohol withdrawal can cause headache, nausea, vomiting, tremors, sleep problems, fatigue, anxiety and other mood changes. Unlike alcohol withdrawal, a hangover can occur after just a single episode of drinking.
Hangovers don’t last as long as alcohol withdrawal, and they don’t include the most severe and dangerous symptoms of withdrawal — hallucinations and seizures.
While researchers are continuing to study the subject, the prevailing theory is that the cluster of symptoms we recognize as a hangover are simply the effects of alcohol on the body.
The way the body breaks down alcohol may account for many of the symptoms. When a person drinks, the liver breaks alcohol down into a chemical called acetaldehyde, which is toxic.
Before the chemical can cause much damage, the body usually breaks it down into another chemical called acetate, which is then converted to water and carbon dioxide and easily eliminated. But when we consume large amounts of alcohol, the liver can’t keep up. Acetaldehyde accumulates, causing nausea and vomiting, sweating and other unpleasant symptoms.
Dehydration also appears to play a significant role in hangovers. Alcohol acts as a diuretic, causing people to urinate much more than usual. As a result, people who’ve drunk too much frequently wake up the next day with a dry mouth, terrible thirst, lightheadedness and a wicked headache.
Alcohol also disrupts natural sleep patterns. While people who consume a lot of alcohol will generally fall into a deep sleep in the early part of the night, later on they’ll shift into a light sleep or even wake up completely. This contributes to next-day fatigue and drowsiness.
Other hangover symptoms are related to the body’s inflammatory response to alcohol and drops in blood sugar that can occur after drinking, according to the Mayo Clinic.
Genetics may also play a role in whether a person is prone to suffer from hangovers. A 2008 study in the journal Current Drug Abuse Reviews found that nearly a quarter of people may be resistant to hangovers. The finding was based on survey results provided by college students, adults in alcohol detox, high school students and adults who have drank heavily and adults in the community who said they’ve been tipsy or high.
The duration of a hangover is typically between eight and 24 hours but can vary widely depending on a number of factors. Severe hangovers can last up to three days.
Generally, the more alcohol you drink, the worse your hangover will be. Drinking on an empty stomach and not drinking enough water can also increase the likelihood of having a bad hangover.
Biological sex, ethnicity, overall health status and liver function can impact the severity and duration of a hangover.
Because of genetic differences, Asian people often have a harder time breaking down acetaldehyde, the main byproduct of alcohol. As a result, they can develop a hangover after consuming smaller amounts of alcohol than people of other ethnic backgrounds. Individuals who suffer from migraine headaches are also more likely to experience hangovers, according to Johns Hopkins Medicine.
The type of drinks you consume can also increase the severity of a hangover. Certain types of alcohol contain high levels of substances known as congeners, which are impurities left behind during the fermentation process when alcohol is made. Dark liquors, such as bourbon, have a high level of congeners. They tend to cause more severe hangovers than light-colored alcoholic beverages such as vodka, which contains no congeners.
The internet is awash in websites promising quick hangover cures, hangover treatments and ways to prevent a hangover. Various remedies touted online include taking vitamins and supplements, consuming greasy food and drinking more alcohol.
So-called IV lounges have also been popping up in cities around the country, promising to cure your hangover with an intravenous infusion of saline, vitamins, minerals, antioxidants and other ingredients. While IV fluid therapy can counter alcohol-related dehydration, medical experts say drinking water is just as effective, and it’s a lot less expensive.
According to a 2005 study in the British Medical Journal, no compelling evidence shows that any sort of treatment can cure or prevent a hangover.
What can you do to relieve the symptoms of a hangover? Mayo Clinic suggests sipping on fruit juice or water to help relieve your dehydration and eating a small snack that’s easy on the stomach. You can also take an over-the-counter pain reliever if you have a headache, but be careful with acetaminophen (Tylenol). It can cause liver damage if taken in conjunction with large amounts of alcohol or by someone who drinks regularly.
If you can, go back to bed and try your best to sleep.
At the end of the day, the only surefire way to prevent a hangover is to drink in moderation or stop drinking altogether. If you or someone you love is struggling with alcoholism and can’t stop drinking, 24-hour alcohol hotlines can connect you with an alcohol rehab center that can help.
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