The science
Why hangovers happen: the science behind the morning after
A hangover is not one thing. It is the sum of several things alcohol does to your body overnight, and knowing them explains why some tips help and others do not.
Written by Darren Lee, Pharmacist · Founder, Attune RX
Published September 30, 2026 · Reviewed September 30, 2026 · 3 min read
Key takeaways
- A hangover has several causes: acetaldehyde, dehydration, broken sleep, inflammation, stomach irritation and a “mini-withdrawal”.
- Darker drinks carry more congeners, which are linked to worse hangovers.
- Because the causes are layered, no single remedy covers them all. Pace, food, water and sleep matter most.
1. Acetaldehyde, the toxic middle step
Your liver converts alcohol into acetaldehyde, then converts acetaldehyde into acetate. Acetaldehyde is toxic and contributes to inflammation in the liver, pancreas, brain and digestive tract.[1] People who carry a common variant of the ALDH2 gene clear acetaldehyde more slowly, which is why some hangover studies focus on this group.[2]
2. Dehydration
Alcohol suppresses vasopressin, a hormone that signals your kidneys to retain fluid. The result is more trips to the bathroom and more fluid lost than usual.[1] Thirst, a dry mouth and a pounding head the next morning are the familiar signs.
3. Broken sleep
Alcohol helps many people fall asleep faster, but it disrupts sleep in the second half of the night.[3] People also tend to wake earlier after drinking, so the day starts tired.[1]
4. Inflammation
Alcohol increases inflammation throughout the body, which feeds the general feeling of being unwell.[1] This is one reason researchers test anti-inflammatory plant extracts: in a prickly pear study, milder symptoms went along with lower levels of C-reactive protein, a marker of inflammation.[4]
5. An irritated stomach and low blood sugar
Alcohol irritates the stomach lining and increases acid release, which can cause nausea.[1] It can also lower blood sugar, which may add to fatigue, weakness and shakiness.[5]
6. A “mini-withdrawal”
Your brain adjusts to alcohol’s calming effect while you drink. As the alcohol wears off, that adjustment can leave you restless and anxious.[1]
7. Congeners
Congeners are by-products of fermentation, more concentrated in darker drinks. In a controlled study, young adults who drank bourbon had worse hangovers than when they drank vodka to the same breath alcohol level.[6]
What this means for the morning after
Because hangovers have several causes, no single fix covers them all. The approach that makes sense is layered: fewer and slower drinks, food, water and sleep first, then support aimed at specific pathways.* That is the thinking behind Good Spirits: DHM for alcohol metabolism, clove extract for oxidative stress, and a B-complex, taurine and choline to replenish what a night out takes.* For a practical plan, see what to take before drinking.
Common questions
Is a hangover just dehydration?
No. Dehydration is one part, but acetaldehyde, inflammation, broken sleep, stomach irritation and a mini-withdrawal all contribute. That is why water alone rarely fixes a bad morning.
Why do dark liquors cause worse hangovers?
They contain more congeners, by-products of fermentation. In one controlled study, bourbon caused worse hangovers than vodka at the same breath alcohol level.
References
- National Institute on Alcohol Abuse and Alcoholism (NIAAA). Hangovers. Updated December 2025. Source
- A standardized extract of the fruit of Hovenia dulcis alleviated alcohol-induced hangover in healthy subjects with heterozygous ALDH2: a randomized, controlled, crossover trial. J Ethnopharmacol. 2017. Source
- Ebrahim IO, et al. Alcohol and sleep I: effects on normal sleep. Alcohol Clin Exp Res. 2013;37(4):539-549. Source
- Wiese J, et al. Effect of Opuntia ficus indica on symptoms of the alcohol hangover. Arch Intern Med. 2004;164(12):1334-1340. Source
- Swift R, Davidson D. Alcohol hangover: mechanisms and mediators. Alcohol Health Res World. 1998;22(1):54-60. Source
- Rohsenow DJ, et al. Intoxication with bourbon versus vodka: effects on hangover, sleep, and next-day neurocognitive performance in young adults. Alcohol Clin Exp Res. 2010;34(3):509-518. Source
*These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure, or prevent any disease. This article is for general education and is not medical advice. Please drink responsibly. Must be 21+.