Most of us will have been there at some point. The pounding headache, nausea, vomiting, maybe a nondescript feeling of anxiety (often accurately dubbed “the horrors”). The hangover experience does not paint a pretty picture, yet time and again, especially over the festive season, we succumb to overindulgence.Given that it is an age-old ailment, the anatomy of a hangover is not scientifically well understood. Very little is known about the physiology, effects, prevention and treatment of alcohol-induced hangover. Whilst tens of thousands of peer-reviewed articles have been published on the acute effects of alcohol intoxication, only a few hundred papers investigate the effects of hangover. Of these articles, there is mixed evidence for a variety of factors that determine how we may react differently to alcohol and hangover.It can often feel that there are no hard and fast rules for working out when a hangover will strike. We might use anecdotal knowledge of individual factors (like age or sex) and prevention or treatment strategies (sticking to one drink, hangover remedies) that we use to make sense of our hangovers. However, is there any evidence behind the anecdotes? Can we engage in any behaviour to cheat a hangover this festive season, or is our fate sealed in our individual make-up?Scientifically speaking, understanding what factors may contribute to a hangover may help us to determine the physiological and behavioural basis of the hangover and how best to prevent, or even cure it. Current evidence, like anecdotal accounts, focuses on individual factors and specific techniques that may influence our experience of hangover. Here I will focus on evidence for two of the most popular anecdotal factors: age and type of alcoholic beverage consumed.AgeMany of us swear that our hangovers are more intense and longer-lasting the older we get. I for one am convinced that it takes me longer to recover from a big night out in my 30s than it did when I was a student in my 20s. Supporting evidence for the effects of age on the experience of hangover suggests we may be onto something.Studies of adult versus adolescent drinkers show that hangover and alcohol withdrawal symptoms are reported less frequently in adolescents relative to adults. In addition, a larger body of animal evidence suggests that adolescent rats are less sensitive to the effects of hangover on anxiety and sociability. Adolescent rats were less anxious, and engaged in more social interactions during alcohol hangover compared with adult rodents.Even aside from the differences between rats and humans, these studies rely on comparisons made between adolescent and adult drinkers. This contrast does not necessarily reflect transitions in alcohol use that occur in an adult’s life (eg going to university, becoming a parent, career changes).Interestingly, a recent large-sample Danish study examining younger and older adult drinkers found that the tendency to experience hangover following an episode of binge drinking decreased with age. The authors suggest that differences in hangover between younger and older adults may reflect differences in binge drinking patterns.The authors caution that whilst younger and older participants had similar average weekly consumption patterns, intensity of drinking was not assessed. It is therefore possible that older adults who binge may consume fewer drinks per binge than younger adults, resulting in fewer and less severe hangovers.Type of alcoholic beverageAnother anecdotal factor in the experience of hangover is the notion that drinking a certain type of alcoholic beverage, or sticking to one type of drink, may prevent or lessen the effects of a night on the town. One reason for why we may experience hangovers of varying intensity after drinking different alcoholic beverages is the amount of congeners in a given drink.Congeners are biological compounds that can be made during the alcohol fermentation process or added during production. A small body of research has suggested that congeners may contribute to the feelings of intoxication we experience, and the subsequent likelihood of hangover.For example, alcoholic beverages with few congeners and higher pure ethanol content (such as gin and vodka) have been shown to induce fewer hangovers than drinks with higher levels of congeners like brandy or red wine (here's a review).  However, this evidence on congeners was conducted in the 70s. Have we come any further in choosing an “ideal” drink for reducing hangover?The study of congeners has slowed considerably since the 70s, but recently it has been revisited by scientists examining the effects of congeners on the neurocognitive effects of hangover. Studying 95 heavy drinkers in a placebo-controlled study of vodka versus bourbon, this research from 2010 found supporting evidence for the 70s studies.Participants reported greater hangover intensity after drinking bourbon (with high congener content) than vodka (low congener levels). But the two drinks did not differ in the effects they had on sleep, reaction time, motor performance, memory and attention the day after drinking. Therefore we may conclude that consumption of different beverages may influence our self-reported hangover the next day (how awful we feel), but will not necessarily affect our performance on everyday tasks such as driving, reading, or concentration in general.The bottom lineThe reality is that we as scientists know very little about the biological basis of alcohol hangover. In particular this area of research is lacking in large scale human studies. So what advice can I give to those who succumb to the dreaded Christmas hangover?Unfortunately, a systematic review published in the British Medical Journal in 2005 does not bear good news. A review of eight randomised controlled trials revealed that there was no convincing evidence for any conventional or complementary interventions for the prevention or treatment of alcohol hangover. The article concludes by advising that the most effective way to avoid a hangover is to drink in moderation or to abstain from drinking alcohol.As far as second guessing a hangover is concerned, it appears the jury is out … sorry! However, the silver lining is that we alcohol scientists have lots more to learn about hangover, and I am more than happy to share what we find. (theguardian.com)ANN.Az