Thirst, headache, faintness, dizziness, nausea and feelings of general lousiness: the clinical symptoms of a hangover. Other than fling yourself in front of marauding elephants, there aren't many better ways to gift yourself the most miserable start to a day or a new year.
But don't write it off as merely just deserts. A hangover knocks your ability to drive to a degree similar if not worse than driving at the legal alcohol limit, says Dr Adele McKinney, a psychologist at Queen's University Belfast who has studied alcohol hangovers. Hangover hits work and academic performance harder than many common medical complaints. It leaves you less able to multi-task and store memories, it disrupts sleep and it lowers mood.
But what's the cause of a hangover? The foremost cause is the neurotoxin alcohol (ethanol) and what the body turns it into (its metabolites). But there's more in the mix. A cocktail of toxins ends up in beers, wines and spirits as a result of fermentation, distillation and ageing processes; these often add distinctive flavours and come from the grains, wine skins or oak barrels. The list of these "congeners" is long – acetone, polyphenols, histamines, tannins, amines, and methanol byproducts are just a few.
"Generally most of these are believed to have a direct effect, probably on the nervous system," says Prof Damaris Rohsenow, a scientist at the Center for Alcohol and Addiction Studies at Brown University, in Rhode Island in the US. She studied the effects of various alcoholic drinks on study volunteers. Of spirits, bourbon had the most congeners, while vodka and gin had the least. Beers differed too, with Budweiser the worst of six she studied. "All six beers had more congeners per standard drink than any liquor did," she says. Of six wines, port wines scored highest, dry white wine lowest.
But vino fans should not feel smug. “The biggest source of a hangover is ethanol, with congeners just ramping up the severity somewhat,” says Prof Rohsenow. “While people felt worse after bourbon than after vodka, those differences were small compared to the effects of getting ethanol.”
Pantomime villain
Not too surprising, but scientists puzzle over how ethanol causes hangover symptoms. Ethanol itself gets turned into acetaldehyde in the body, a toxin that was early on cast as a pantomime villain. Not guilty, says Prof Rohsenow, because the hangover drum pounds most intensely after all the acetaldehyde is gone from the blood.
“People felt acetaldehyde is such a reactive and toxic compound that it is responsible for the alcohol-induced headache,” says neuroscientist Dr Micheel Oshinsky, migraine researcher at NIH’s National Institute of Neurological Disorders and Stroke in Maryland. ‘But we showed that wasn’t the case.’
The body dislikes acetaldehyde, so the liver quickly turns it into acetate, a natural, energy-rich compound in the body. When Oshinsky’s lab fed enough acetate to rats, they got a headache (How do they know? For one, rodents with headaches are 12 decibels more sensitive to loud noises). Acetate is a compound with a characteristic sweet smell: it is used in glues and nail polish removers.
The bonanza of acetate eventually triggers a spike in a neurotransmitter called adenosine, especially in a part of the brain which processes pain signals. This ramps up sensitivity to headache, says Oshinsky, who began this research to investigate the role of disordered acetate metabolism in people suffering from migraine.
Coffee cure
One way to help the acetate-laden rodents is to dose them with caffeine. In fact Oshinsky’s lab discovered that feeding them caffeine four hours after giving them alcohol warded off their impending headache. This is because caffeine blocks their adenosine receptors in the brain. The conclusion: caffeine is one way to diminish an alcohol headache, with its effects lasting two hours. But there is more to a hangover.
Recent research suggests ethanol can play havoc with our inflammatory system. "Pro-inflammatory cytokines are elevated for some hours after heavy drinking," says Prof Rohsenow.
Alcohol also increases the amount of the hormone vasopressin, which causes you to pee more. Prof Rohsenow believes dehydration due to changes in this hormone “may play a minor role”. Her own research has shown that alcohol-induced sleep disturbance is yet another contributor to a hangover, delivering a dose of jetlag.
And it still doesn’t end there. Methanol is found in small quantities in most tipples and the substances it gets broken down into – such as formic acid – may worsen your hangover.
All this complexity is bad news for those hoping to rely on one of the many internet miracle cures. It is not surprising that none truly work. The real, perhaps not very jolly, cure is to imbibe less ethanol. If moderation fails, a glass of juice, breakfast and a big mug of coffee or pot of tea are your best options.
Double the trouble: cigarettes and alcohol
Smoking while drinking will worsen your hangover, research shows.
“We think this is due to the immediate action of nicotine in the brain,” says Prof Damaris Rohsenow at Brown University in the US. “This is possibly because nicotine constricts blood vessels in the brain or it could be due to some of the great many other effects of nicotine in the brain. The exact mechanism is unclear.”
Student drinkers filled out a survey about drinking, smoking and hangovers every day for eight weeks, with 94 per cent of the entries completed.
“We looked at the nights when the students drank enough to result in an estimated blood alcohol level of at least 0.11per cent, and their hangover ratings the next morning,” says Prof Rohsenow.
“Since people smoke more on days that they drink more, we statistically controlled for the numbers of drinks they had when looking at the relationship of smoking to drinking,” she explains. “We found that people who smoked more cigarettes but had the same number of drinks as someone else would be more likely to feel hungover the next morning and to report a more intense hangover.”
Finally, Prof Rohsenow offers no festive cheer to people who are less sensitive to alcohol intoxication. Those people, who can “hold their drink,” are fortunate in that they also suffer less of a hangover for a given amount of alcohol. But people less sensitive to hangovers in college tend to report more drinking problems later in life, Prof Rohsenow’s research has shown.