"Grape or grain, but never the twain." So runs the old folk wisdom that advises against drinking wine or beer on the same night. It is far from uncommon to hear people who have woken up feeling sick, dehydrated and with a splitting headache blaming their hangovers on having unwisely mixed their drinks. 
 
 Then there are the theories about the order in which to consume different tipples. One version suggests: “Wine before beer and you’ll feel queer. Beer before wine and you’ll feel fine.” Or is it the other way round? After a couple of drinks it’s not always easy to remember. All of which begs the question of how reliable these sayings are. Is there any evidence beyond the anecdotal that drinking wine followed by beer or vice versa makes hangovers worse? 
 
 A review of previous research published in 2000 confirms that the causes of the main symptoms of hangovers are dehydration, changes in the levels of hormones such as aldosterone and cortisol, and the toxic effects of alcohol itself. In addition there’s evidence that the immune system is disrupted and that this could be the cause of the headache, the nausea and the fatigue. 
 
 
 
 The first of the two main ingredients of a drink that affect the severity of a hangover is obvious. The higher the alcohol content, and the faster you drink it, the worse the hangover. This is however just an average. The same quantity of alcohol does not always result in the same severity of hangover. Many report that they don’t get hangovers and no one quite knows why. In a study of young Danes on holiday, almost a third of those who consumed at least 12 units of alcohol (roughly equivalent to four pints of lager or four 250ml glasses of wine) avoided hangovers. 
 
 Mixing drinks needn’t necessarily increase the overall amount of alcohol consumed, but it may do with cocktails. If combining three or four measures of spirits alongside other ingredients, a throbbing head and dry throat is probably just the result of consuming more alcohol in total. 
 
 Beyond the ethanol that triggers intoxication, the other key ingredients that affect hangovers are what the beverage industry calls congeners. These are the other substances produced during fermentation, such as acetone, acetaldehyde, fusel oil and the best-known, tannins, which give darker drinks their colour and part of their flavour. Bourbon whisky, for example, contains 37 times the quantity of congeners as vodka. 
 
 To find out the effect of these substances on hangover severity, researchers in the US recruited university students who were regular drinkers, without alcohol problems. On different nights they were given either bourbon and cola, vodka and cola or a placebo which consisted of cola mixed with tonic, with a few drops of either bourbon or vodka to make it taste similar to the real stuff. They drank anything between three and six drinks, however much was enough to give them a concentration of 0.11g of alcohol per 100ml of breath. This would put them two to five times over the drink drive limit, depending which country they were in. They then spent the night in the clinic and were woken at 7am for breakfast before taking part in a battery of tests. For this they were paid a rather generous $450. The researchers found the students who drank bourbon rated their hangovers as worse, but interestingly they performed just as well on tasks such as reaction time tests. 
 
 Clear drinks such as white rum, vodka and gin tend to cause fewer and less severe hangovers because they contain relatively low levels of congeners. Perhaps those who mix their drinks are more likely to choose a dark-coloured drink containing higher levels of these substances simply by virtue of their wider drinking range, but again it isn't the mixing in itself that causes the problem. 
 
 No scientist seems to have done the perfect counter-balanced study where people are randomly assigned to drink beer followed by wine or wine followed by beer. But perhaps it’s not the grape or the grain that matters, but the effect that the strength of those drinks has on judgement. Beer is only between a third and half the strength of wine, so starting on it leads to less intoxication if followed by the stronger stuff. But if a person starts on wine or spirits, then their judgement may be impaired enough to drink more heavily later. There’s certainly evidence that people are not good at judging their own drunkenness. At low levels people overestimate the amount of alcohol in our blood, but after a few drinks they start to underestimate it. 
 
 So, the existing evidence suggests that hangovers can't be blamed on mixing drinks. It's probably down to the high congener count of the booze, or over-drinking. As for hangover cures, scientists have looked into those too, and the British Medical Journal published a review of trials of everything from borage to artichoke and glucose to prickly pears in 2005. The bad news for drinkers is that none of them work. 
 
 Do you agree? If you would like to comment on this, or anything else you have seen on Future, head over to our Facebook or Google+ page, or message us on Twitter. ||||| Some people get hangovers after a night of drinking, while others don't, and the reason may be in their genes, a new study of twins in Australia suggests. 
 
 Researchers looked for links between the study participants' genetic makeups and the number of hangovers the individuals reported experiencing in the past year. The results showed that genetic factors accounted for 45 percent of the difference in hangover frequency in women and 40 percent in men. 
 
 In other words, genetics accounts for nearly half of the reason why one person experiences a hangover and another person doesn't, after drinking the same amount of alcohol, the study said. The other half probably comes from outside influences unrelated to DNA, such as how quickly a person drinks, whether they eat while they drink and their tolerance for alcohol. 
 
 The researchers also found that the people who had the gene variants involved in an increased risk of having hangovers also drank to the point of being intoxicated more frequently than people who didn’t have the hangover genes. That is, the genes that dictate how frequently a person gets hungover may also underlie how frequently someone gets drunk in the first place. This suggests that the findings could contribute to future research on alcohol addiction. 
 
 "We have demonstrated that susceptibility to hangovers has a genetic underpinning. This may be another clue to the genetics of alcoholism," study leader Wendy Slutske, a psychology professor at the University of Missouri-Columbia, told Live Science in an email. [7 Ways to Cheat a Hangover] 
 
 People who are less susceptible to having a hangover might have a greater risk for alcohol addiction, the researchers said. 
 
 In the study, about 4,000 middle-age people from the Australian Twin Registry participated in a telephone survey, reporting their experiences with hangovers and alcohol consumption. The participants recounted how many times they had gotten drunk in the past year, along with their "hangover frequency," which is the number of days in the previous year they felt sick the day after drinking. They also reported their "hangover resistance," which was whether or not they had ever experienced a hangover after getting drunk. 
 
 The researchers found a strong correlation between identical twins in reports of hangover frequency as well as hangover resistance, suggesting that the genetic similarities of some twins played a part in their hangover susceptibility. 
 
 Research into the biology of hangovers has gotten more attention in recent years, but there's still surprisingly little work on the topic, Slutske said. 
 
 "With drinking alcohol, it is not 'one size fits all,'" Slutske said. "People are different in their ability to consume alcohol without experiencing adverse consequences, such as having a hangover." 
 
 The new findings suggest that people who frequently consume alcohol should observe the way their bodies react to it, she said. "It is not a good idea to try to pace your drinking to the people around you, because you might be more susceptible to hangover than the other people that you are drinking with," Slutske said. 
 
 The study was limited, because people's memories of their drinking and hangovers may not be completely accurate, she noted. 
 
 One of the next steps will be to identify the specific genes that contribute to hangover susceptibility, Slutske said. If the genes associated with alcoholism also underlie hangovers, identifying these genetic risk factors could help prevent addiction in the future. 
 
 Follow Jillian Rose Lim @jillroselim. Follow us @livescience, Facebook & Google+. Original article on Live Science.
– Many of us may avoid downing hard alcohol, wine, and beer on the same night for fear of a raging hangover the next day. But at the BBC, a review of existing research on the topic suggests the drinks' variety itself isn't the problem. Instead, Claudia Hammond points to other possible factors. For instance, she notes, having several different types of drinks may simply mean drinking more total alcohol. (As for "beer before liquor, never been sicker"? It appears no research has been done to prove or disprove the idea that drink order makes a difference.) "The existing evidence suggests that hangovers can't be blamed on mixing drinks," Hammond writes. But the amount of alcohol may not be the only culprit: Congeners, the non-ethanol products of the fermentation process, also contribute to a hangover. Tannins, for instance, are responsible for the color in darker types of alcohol. There are 37 times more congeners in bourbon than in vodka, and one study found that bourbon drinkers reported worse hangovers than those who drank vodka. So, Hammond writes, people having various types of drinks in a single night may end up indulging in drinks with more tannins. So go ahead and mix types of alcohol if you so desire, but you may want to avoid mixing alcohol with cigarettes: A study last month found that people who smoke and drink are at a higher risk of developing esophageal cancer, Science Daily reported. (If you do find yourself with a hangover, you may want to reach for a Sprite.)