You did everything the internet told you to. Water between rounds, a big meal first, an electrolyte drink before bed. You still woke up at 6 a.m. feeling scraped out. So what causes a hangover, really — and why do the standard fixes fail so reliably?
The honest answer from the peer-reviewed literature is less satisfying than the folklore, and more useful. The strongest single predictor of how bad tomorrow feels is how much ethanol you drank tonight. Everything else — acetaldehyde, congeners, dehydration, inflammation, broken sleep — modifies that picture, some with real evidence behind them and some with almost none. Here is what holds up.
What causes a hangover: the five mechanisms on the table
Researchers have proposed and tested five main culprits. They are not equally supported:
- Acetaldehyde — the toxic first product of alcohol metabolism. Popular, but the human correlations are inconsistent.
- Congeners — flavour and colour compounds from fermentation and barrel ageing. A real but secondary effect.
- Dehydration — measurable, and largely a separate problem from the hangover itself.
- Inflammation — the strongest biomarker signal so far, from very small studies.
- Sleep disruption — the most consistently replicated effect in the whole literature.
Acetaldehyde: the mechanism everyone names
Your liver converts ethanol to acetaldehyde, then acetaldehyde to acetate. Acetaldehyde is genuinely toxic, so the story writes itself. The trouble is that the story does not survive measurement well. In their review of hangover pathology in Current Drug Abuse Reviews, Penning and colleagues (2010) found that while some studies report a correlation between blood acetaldehyde and hangover severity, the findings across studies are inconsistent. In the biomarker data compiled by van de Loo and colleagues (2020), acetaldehyde showed no significant association with hangover severity at all, while immune markers in the same participants did.
Acetaldehyde is probably part of the chain — it is what drives the flushing reaction in people with reduced ALDH2 enzyme activity — but the evidence that it is the direct cause of your headache is weaker than its reputation suggests.
Congeners: what the bourbon-versus-vodka study actually found
This is the congeners hangover study people half-remember. Rohsenow and colleagues (2010), published in Alcoholism: Clinical & Experimental Research, ran 95 healthy heavy drinkers aged 21 to 33 through drinking sessions to roughly 0.11 g% breath alcohol concentration, on bourbon or vodka, each matched against placebo on another night, randomised for beverage type and order.
Two results matter, and most write-ups only report the first. Yes, bourbon produced worse subjective hangovers than vodka. In their companion review, Rohsenow and Howland (2010) put it plainly: "the highest congener beverage (bourbon) results in more severe hangover ratings than does the beverage with essentially no congeners (vodka)" — while noting that ethanol itself had a considerably stronger effect on hangover than congener content did.
The second result is the one to take home. Next-day neurocognitive performance was impaired about equally after both drinks. Feeling less rough is not the same as being less impaired. So the clear spirits hangover advantage is real but narrow: it may change how tomorrow morning feels, and it does not change how much alcohol you drank or how well you will function.
Dehydration is real — it just isn't the hangover
Alcohol suppresses vasopressin, you make more urine, you get thirsty. All true. But Penning and colleagues found no significant relationship between vasopressin and other dehydration markers and hangover severity. More recently, Mackus and colleagues (2024), writing in Alcohol, revisited the question directly and reported that drinking water during or immediately after alcohol had only a modest effect on next-day hangover, and that water consumed during a hangover showed no relationship to symptom improvement. Their conclusion is that dehydration and hangover are "two co-occurring but independent consequences" of drinking — dehydration being mild and short-lived, the hangover enduring.
Drink the water. It fixes thirst and dry mouth, which are genuinely unpleasant. Just do not expect it to fix the headache.
Inflammation: the strongest signal, from the smallest studies
The most promising mechanism is immune. van de Loo and colleagues summarised two biomarker studies: in Kim et al.'s sample of 16 participants, TNF-α at 4 hours correlated with hangover severity at r=0.679 and IL-6 at 12 hours at r=0.459; in Mammen et al.'s sample of 13, C-reactive protein at 4 hours correlated at r=0.534. Penning and colleagues likewise concluded that immune factors, not dehydration or metabolic disruption, best explain hangover severity on current evidence.
Note the sample sizes: 16 and 13. These are correlations in tiny groups, not proof of causation, and they have not been replicated at scale.
Sleep disruption: the most reliably measured effect
Alcohol is a sedative that stops working halfway through the night. In the Rohsenow trial, alcohol reduced sleep efficiency and REM sleep and increased wakefulness and next-day sleepiness — and critically, sleep disruption did not fully account for the cognitive impairment observed. A 2025 systematic review and meta-analysis in Sleep Medicine Reviews by Gardiner and colleagues, pooling 27 studies, found REM sleep disruption at doses as low as roughly two standard drinks, worsening progressively with higher doses.
Hangover cures: the evidence, including what failed
The single best summary of hangover cures evidence is still the systematic review by Pittler, Verster and Ernst (2005) in the BMJ. They found 15 potentially relevant trials, of which 8 randomised, double-blind controlled trials of 8 different interventions met inclusion criteria: propranolol, tropisetron, tolfenamic acid, fructose or glucose, and the supplements borage, artichoke, prickly pear and a yeast-based preparation.
Only three — tolfenamic acid, gamma-linolenic acid from borage, and the yeast preparation — showed any significant differences on symptom scores. The authors' conclusion: "No compelling evidence exists to suggest that any conventional or complementary intervention is effective for preventing or treating alcohol hangover." Note what is absent from the list of things that worked: sugar loading, artichoke extract, and prickly pear all failed to clear the bar.
What you can actually do today
- Manage the dose. Ethanol quantity outweighs every other variable in these studies. This is the lever that actually moves.
- Protect the back half of your sleep. Stop drinking well before bed rather than right at bedtime.
- Drink water for thirst, not as insurance. The 2024 evidence says it will not buy you the morning you are hoping for.
- Don't trust how you feel. The Rohsenow data showed equal next-day impairment regardless of which spirit was drunk. Plan tomorrow accordingly.
What the research does not show
Be sceptical of anyone — including us — who overreads this literature. The biomarker studies are tiny. The congener finding comes from a small number of experiments, and its own authors called for more research before treating it as settled. The 2005 BMJ review is two decades old, and most of the trials in it were small and short. Nothing here shows that any drink is safer, healthier or less intoxicating than another. A gram of alcohol is a gram of alcohol.
That applies to us too. Aura is a still, canned vodka water made with premium distilled vodka, alkaline water and natural flavour — no carbonation, no added sugar, no artificial sweeteners. Vodka is a low-congener clear spirit, and our cans are sold at a fixed size so you always know exactly what you've had, which makes counting your drinks easy. Neither of those is a health claim, and neither reduces the alcohol in the can. Canada's Guidance on Alcohol and Health (CCSA, 2023) places 1–2 drinks per week at low risk, 3–6 at moderate risk and 7 or more at increasingly high risk, and advises no more than 2 standard drinks on any single occasion.
This article summarises published research for general interest and is not medical advice.
If a still drink with no bubbles and no bloating sounds like your kind of evening, take a look at our vodka water cocktails, read why Aura, or find where to buy across British Columbia, Alberta and Ontario. Must be of legal drinking age in your province. Please enjoy responsibly.
Sources
- Penning R, van Nuland M, Fliervoet LAL, Olivier B, Verster JC. The pathology of alcohol hangover. Current Drug Abuse Reviews. 2010;3(2):68–75. PMID: 20712596. DOI: 10.2174/1874473711003020068. pubmed.ncbi.nlm.nih.gov/20712596
- Rohsenow DJ, Howland J. The role of beverage congeners in hangover and other residual effects of alcohol intoxication: a review. Current Drug Abuse Reviews. 2010;3(2):76–79. PMID: 20712591. DOI: 10.2174/1874473711003020076. pubmed.ncbi.nlm.nih.gov/20712591
- Rohsenow DJ, Howland J, Arnedt JT, Almeida AB, Greece J, Minsky S, Kempler CS, Sales S. Intoxication with bourbon versus vodka: effects on hangover, sleep, and next-day neurocognitive performance in young adults. Alcoholism: Clinical and Experimental Research. 2010;34(3):509–518. PMID: 20028364. DOI: 10.1111/j.1530-0277.2009.01116.x. pubmed.ncbi.nlm.nih.gov/20028364
- Pittler MH, Verster JC, Ernst E. Interventions for preventing or treating alcohol hangover: systematic review of randomised controlled trials. BMJ. 2005;331(7531):1515–1518. PMID: 16373736. DOI: 10.1136/bmj.331.7531.1515. pubmed.ncbi.nlm.nih.gov/16373736
- Mackus M, Stock A-K, Garssen J, Scholey A, Verster JC. Alcohol hangover versus dehydration revisited: the effect of drinking water to prevent or alleviate the alcohol hangover. Alcohol. 2024;121:9–18. PMID: 39069212. DOI: 10.1016/j.alcohol.2024.07.006. pubmed.ncbi.nlm.nih.gov/39069212
- van de Loo AJAE, Mackus M, Kwon O, et al. The inflammatory response to alcohol consumption and its role in the pathology of alcohol hangover. Journal of Clinical Medicine. 2020;9(7):2081. PMID: 32630717. DOI: 10.3390/jcm9072081. pmc.ncbi.nlm.nih.gov/articles/PMC7408936
- Gardiner C, Weakley J, Burke LM, Roach GD, Sargent C, Maniar N, Huynh M, Miller DJ, Townshend A, Halson SL. The effect of alcohol on subsequent sleep in healthy adults: a systematic review and meta-analysis. Sleep Medicine Reviews. 2025;80:102030. PMID: 39631226. DOI: 10.1016/j.smrv.2024.102030. pubmed.ncbi.nlm.nih.gov/39631226
- Canadian Centre on Substance Use and Addiction. Canada's Guidance on Alcohol and Health. 2023. ccsa.ca/en/canadas-guidance-alcohol-and-health