One friend says tequila is her downfall. A couple of shots and she becomes a raging sex maniac, unable to control herself around men. Another friend says he gets angry on beer and mellow on scotch. Over the years he’s become the slow-sipping guy with a private smile sitting quietly on his barstool.  An acquaintance tells me she gets seriously bad hangovers from every version of alcohol — wine, beer, whisky, cocktails — with one exception; she wakes up fresh after drinking vodka and cranberry poured into a clinking glass of ice. Raise ‘em high!

We all believe — or have friends who swear — that different alcohols produce different effects, whether on our present mood, our sleep, or the next day’s hangover. But how do scientists weigh in on this age-old matter; are some alcohols truly worse for you than others?

Let’s take it from the top. No matter the drink, it contains the same active ingredient: ethanol. It’s your liver’s job to filter the blood coming from your digestive tract, and this includes processing alcohol-laden blood after you down a glass of wine, beer, or spirits. But while it may be an efficient and wondrous organ, your liver can only handle so much alcohol at a time. When it becomes overloaded — this happens quickly since our bodies respond to alcohol as a poison — the excess ends up circulating in your bloodstream and traveling to every organ in your body, including the brain. The result: giggly intoxication.

When it comes to these physical effects, then, the crucial factor is the alcohol concentration in the glass you raise to your lips. The amount of alcohol in each sip will determine how difficult it is for your liver to absorb and process it. That said, other ingredients in the drink may also contribute to your liver’s ability to process it, as well as the sensations you feel. Essentially, any impurities in poorly produced brands of alcohol can amplify its effects, yet the most important of these influential components are congeners.

Hangovers Dissected

In Latin, congener means “born together.” These organic molecules are produced during the fermentation process, and contain small amounts of chemicals, including methanol, other alcohols, tannins, esters, and acetone, among others on a long list. While they are more commonly found in darker drinks, they contribute to the taste and aroma of all alcoholic beverages — their levels vary depending on the alcohol type and brand.

These substances also add to the symptoms of a hangover — the groggy, headache we feel in the morning after drinking too much. While hangovers don’t kill you, they are a symptom of poisoning because your blood is meant to convey oxygen, not alcohol, to your organs and tissues. For this reason, it’s safe to say that any alcohol containing higher levels of congeners will probably be worse for your hangover and your health than those containing lower levels.

Scientific proof of the negative health effects of congeners can be found in one 2010 study pitting bourbon against vodka, a drink with more congeners versus one with less. The researchers found bourbon was twice as likely to cause sickness as an equal amount of vodka. That said, congeners impacted only the severity of hangovers and did not influence participants’ sleep or next day performance on tests. Regardless of what they drank, participants performed equally poorly on tests requiring sustained attention and speed, and showed an equivalent decrease in sleep efficiency and REM sleep. These results applied to both men and women, the researchers concluded.

Good Work If You Can Get It

If you’re imagining what it would be like to have scientists hand you a paycheck for hanging out and drinking all day, you don’t have to imagine anymore. It turns out that a number of scientific studies pay numerous volunteers to drink (good luck finding one). Often, this happens in a laboratory, at other times in a congenial group of other paid volunteers — all in an effort to understand the effects of alcohol.

For example, a 2016 brain scan study involving only men suggests your personal drinking history may contribute to how you behave when drinking. Researchers compared heavy and normal drinkers, and found the heavy drinkers had more functional brain connections in their cerebellum, which plays a role in muscle coordination. By contrast, normal drinkers showed more wiring in their visual and prefrontal cortices, which influence vision and decision-making; the default mode network, active when we daydream; and the thalamus, which regulates sleep and consciousness. The reduced connections in heavy drinkers contributes to a decline in their mental abilities, the researchers said, while the increased cerebellar connectivity may have compensatory effects on their behavior, perhaps causing them to “act out” more than an average person.

Another study worked to dispel the myth that one drink or another might cause a particular mood or behavior, such as anger or sex mania. Drinking either vodka or bourbon for nine days running, participants showed no consistent differences in their behavior. Soberly observing from the sidelines, the researchers found both drinks caused participants to be more sociable at first, yet soon enough, the participants sank into anxiety, depression, and hostility. And, no matter whether the magic carpet ride was vodka or bourbon, those who got the most drunk from either beverage eventually became grossly psychotic.

However, a 1997 study refuted these results and supports the theory that “different alcohols affect people differently” — at least in the short term. In this study, experimental psychologists pitted beer against what the researchers described as a “blue, peppermint concoction” of exactly equal alcohol concentration. Interestingly, the study participants who drank the unfamiliar blue concoction, though they absorbed the same amount of alcohol, performed significantly worse on both motor and cognitive tasks, and rated themselves more intoxicated than the beer drinkers. According to the researchers, the familiar drink (beer) arouses familiar cues that we respond to in a conditioned and more tolerant way.

In the end, lessons from biology and psychology suggest that different alcohols do have some different effects due to both concentration levels of alcohol and some other ingredients, primarily congeners. Still, the allure of the unfamiliar may temporarily go to our heads as much as the alcohol itself.