Hangovers: What science says about why you feel so rough


Why do I feel so bad?

Alcohol. Undoubtedly alcohol. Your headache, nausea, sweats, tiredness, apathy, that nebulous sense of guilt – they indubitably come from drinking too much last night.

But then again, not alcohol. The onset of a hangover means your blood’s concentration of ethanol – the alcohol we appreciate for its intoxicating qualities – is zero, or fast approaching it. This paradox is the central mystery of the hangover.

What’s going on inside me?

That’s unclear. There probably isn’t just one cause for all the recognised hangover symptoms (see “47 ways not to love your liver”). Some may be only indirectly related to alcohol consumption: fatigue, for example, could be down to burning the midnight oil or busting too many moves on the dance floor. Or it could be the impact on sleep quality of forcing your body to break down a large amount of fluid sustenance – not to mention a late-night takeaway – just before bedtime.

Others, like dehydration, are side effects. Your pounding head and mouth like a wrestler’s jockstrap probably result from alcohol’s suppression of the antidiuretic hormone vasopressin, a process that makes you pee more. During the hangover vasopressin snaps back to a higher level than normal, although there appears to be no correlation between that, or indeed any other drink-induced hormonal imbalance, and the severity of the hangover.

As for the rest, it’s largely educated guesswork. The delayed onset of a hangover means that the metabolic products of ethanol are prime suspects. A 2005 study in Japan found that people with inactive genes for making enzymes that break down acetaldehyde, a highly reactive by-product of ethanol, experienced a hangover after fewer drinks.

Then again, an earlier Scandinavian study showed that acetaldehyde concentrations were generally low when a hangover was most severe. This suggests its effects, too, are indirect or delayed – pointing the finger further down the line, perhaps to acetate, a product of acetaldehyde breakdown.

None of which is particularly helpful.

Was it how much I drank?

Not necessarily. Recent analysis of the urine of a group of hung-over Dutch students did find that ethanol concentration was correlated with severity of symptoms including sleepiness, sweating, concentration problems, nausea, thirst and, to a lesser extent, confusion, headache, weakness and regret. The same correlations were not present in a self-described hangover-immune group that had drunk a similar amount. People in this latter group also had less alcohol in their urine.

This suggests that the ability to rapidly metabolise alcohol is more important than the amount consumed in determining hangover severity. (Sadly, there is no known way to acquire such a skill.) But it doesn’t explain why we can have a hangover like the end of days when we hardly drank anything, and at other times can have a skinful and get off lightly. “Only few studies examined this topic and reported inconclusive results,” the authors of the Dutch study observed – a common refrain in hangover research.

Was it what I drank?

Possibly. Various studies have looked into the role of “congeners” – chemicals produced during fermentation, other than ethanol, that give each alcoholic drink its distinctive aroma and taste. Are dark spirits worse than clear ones? Yes, according to a 2009 study that compared hangover severity in bourbon and vodka drinkers. The higher levels of congeners in mature whiskies, on the other hand, might inhibit the breakdown of ethanol and at least delay the onset of hangover, according to research from Japan.

The trouble is, these experiments were done in mice. In any real-life human scenario, by the time you’ve got on to the single malts, the damage has probably already been done.

Was it how I drank it?

This is the Achilles heel of the already flimsy body of hangover research. There are too many variables in how we actually go about creating hangovers in the wild for researchers to reliably establish correlations. Asking people the next morning how much they actually drank and in what order – plus a host of other possibly relevant factors such as whether they drank water, when and what they ate, their mood, the company they kept and so on – is also fraught with imponderables.

sweeping bottles

Maybe those last few bottles weren’t such a good idea

SSPL/Getty Images

So, “beer after wine and you’ll feel fine; wine after beer and you’ll feel queer”? No one knows. Anyone inclined to cite those particular words of wisdom, however, please note: the Germans, who know a thing or two about drinking, have a similar proverb, just the other way round.

Am I getting too old for this sort of thing?

In a general sense, yes. Most hangover research is conducted on university students, a ready pool of guinea pigs who exhibit the right behaviours. But there has not yet been a study with a statistically large enough sample to say whether hangover symptoms and severity change with age. Other factors, such as fitful sleeping patterns, are probably more significant in contributing to perceived hangover severity than a heightened sensitivity to alcohol.

What can I do to cure a hangover?

Very little. If you’re feeling the after-effects, drinking water will alleviate dehydration-related symptoms. There is no evidence, however, that depleted levels of electrolytes such as sodium, potassium and magnesium are correlated with hangover severity. So an isotonic drink the morning after is likely to have nothing more than a placebo effect. Placebo can be powerful, however – even when you know it’s placebo. Given the absence of a scientifically verified cure, do what works for you, whether that’s strong coffee or a fatty fry-up.

Hair of the dog?

Possibly not that. According to a theory that has done the rounds in recent years, many hangover symptoms are correlated with the breakdown not of ethanol, but methanol, a common congener in many alcoholic drinks. Given the choice, the enzymes that break down alcohol go for ethanol rather than methanol, so flush a little more ethanol through your system when the hangover kicks in and you’ll find some temporary relief – or so the theory goes. The effect has yet to be replicated in any reliable study.

Any cure?

Don’t drink so much. That is to say, no, there is no cure. And it’s unlikely we’ll get one until we understand the pathology of hangovers.

When is science going to give us some answers?

Possibly never. Hangover researchers have three options, all of them flawed. First, experiments in other animals, which are both ethically suspect and of questionable validity, given the uniquely human factors that contribute to the creation of hangovers. Second, laboratory experiments with willing volunteers under controlled conditions. These again fail to reproduce environmental factors and also introduce an observer effect: people do not behave normally if they know they are being watched. Third, self-reporting of hangover symptoms combined with tests performed the morning after – about the last time anyone is capable of supplying reliable answers.

All this, plus the fact that no one wants to be seen as condoning or encouraging alcoholic overindulgence, means we’re likely to be on our own here. A hangover is nature’s way of telling you not to do it again. So, being human, you’ll go out and do it again.

This article appeared in print under the headline “Regrets? I’ve had a few…”


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