Do you ever wake up after a night on the booze, heart pounding, with the feeling that the world is ending and everyone hates you? If you’re someone who experiences hangover-related anxiety (often nicknamed hangxiety or beer fear), you’re probably keen to know why this happens. So, let’s break down the science.

How alcohol affects the brain

Consuming alcohol affects various systems of neurotransmitters, which are chemicals that neurons use to communicate with each other. The ones we’re focusing on today are gamma-aminobutyric acid (GABA) and glutamate.

“The balance of the tone of glutamate and GABA activity within the brain is the primary regulator of the balance of excitation and inhibition in brain circuits,” John H. Krystal, MD, chair of psychiatry at Yale and co-director of the National Institute on Alcohol Abuse and Alcoholism (NIAAA) Center for the Translational Neuroscience of Alcohol, told IFLScience.

First off, let’s talk about GABA. This is an inhibitory neurotransmitter, reducing a neuron’s response to stimuli (aka lowering its excitability) when it binds to GABA receptors. It is “the main inhibitory chemical messenger in the cerebral cortex, primarily responsible for providing inhibitory tuning of the activity of glutamate neurons,” Dr Krystal explained.

GABA signaling in the brain is thought to have a role in reducing fear and anxiety. Some drugs used to treat anxiety disorders, such as benzodiazepines, act on GABA receptors. GABA is produced when glutamate is converted into it via an enzyme – and glutamate is our next topic.

Unlike GABA, glutamate increases the excitability of neurons. “Glutamate is the main excitatory transmitter for the cerebral cortex, accounting for about 90 percent of the synaptic communication between nerve cells. In many ways, glutamate is the main ‘information highway’ of the brain,” said Dr Krystal. It binds to a range of receptors, including N-methyl-D-aspartate (NMDA) receptors.

Glutamate plays a key role in many functions such as pain signaling, as well as memory and learning. Dr Krystal told IFLScience that panic attacks and increased anxiety can result from too much activation from glutamate.

So how does alcohol affect these neurotransmitters?

“Alcohol intoxication at low levels produces a mix of pro-GABA and pro-glutamate effects. With higher levels of intoxication, the pro-GABA effects start to be combined with the ability of alcohol to block the NMDA type of receptor,” Dr Krystal explained. “Together, these effects contribute to the mood effects and cognitive impairments associated with alcohol intoxication. At still higher doses the inhibition of excitation dominates producing sleep and, at toxic doses, potentially life-threatening coma.”

Why might you feel anxious while hungover?

“Alcohol may reduce anxiety by inhibiting responding to anxiety provoking stimuli,” write the authors of a 2019 study. “The anxiolytic [anxiety-reducing] effect of alcohol may influence the SAD-AUD [social anxiety disorder-alcohol use disorder] link and is thought to mediate coping-motivated drinking.”

Dr Krystal told IFLScience that although having too much GABA activation when you’re drunk can alleviate anxiety, it “may also create a form of fearlessness that inappropriately disinhibits behavior,” which you have probably witnessed if you’ve spent any significant amount of time around drunk people (or even experienced yourself).

So if alcohol can reduce anxiety while you’re intoxicated, why might you feel so horrendous mentally the next morning?

After a period of having more GABA signaling and less glutamate signaling than usual, the brain has to rectify this imbalance somehow, adapting neurotransmitter systems accordingly and changing the populations of their receptors.

As Dr Krystal described, tolerance to alcohol and physical dependence on it can develop after long-term heavy drinking due to these neurological changes that the brain is making to try to restore equilibrium. When someone stops drinking after this has happened, some unpleasant effects can happen while the brain tries to get back on balance.

“When alcohol is withdrawn, the GABA receptors are less functional, producing less inhibition, resulting in increased excitation. Similarly, the NMDA glutamate receptors adapt to their chronic blockade by alcohol by increasing their numbers, reducing the sensitivity of the population of NMDA receptors to alcohol,” Dr Krystal explained.

“When alcohol is withdrawn and more glutamate is being released due to reduced GABA inhibition, the glutamate that is released is seeing higher numbers of NMDA receptors and that glutamate is, as a result, even more effective in producing anxiety and, in severe cases, seizures and damage to nerve cells.”

Alcohol withdrawal syndrome (AWS) occurs when someone who has been regularly drinking heavily suddenly stops or decreases their alcohol intake, with symptoms starting around eight to 24 hours after their last drink. The likelihood of experiencing symptoms – which include anxiety, a rapid heart rate, shakiness, mood swings, irritability, and nightmares, as well as more dangerous ones such as seizures and delirium tremens – increases the more you regularly drink.

“A person who is not a regular drinker, but who has a big alcohol binge, experiences a very mild form of the alcohol withdrawal syndrome on top of the other consequences of alcohol intoxication, such as dehydration, irritation of the lining of the stomach and intestines, and impaired sleep,” said Dr Krystal. On top of this, alcohol metabolites like acetone and acetaldehyde can also make you feel rather bad.

“The appearance of mild alcohol withdrawal symptoms following a binge may contribute symptoms including increased anxiety, consistent with increased excitability of the amygdala, and a heightening of responses to sensory stimuli, consistent with increased cortical excitability,” he continued. “These signs and symptoms of hangover are consistent with the notion that some mild forms of GABA and glutamate adaptations to alcohol can occur in a single bout of heavy drinking.”

Dr Krystal explained that some heavy drinkers “have been self-medicating pre-existing anxiety problems with alcohol. Further, heavier drinkers are more likely to experience more significant withdrawal symptoms within a day or two of the end of a binge,” and that his clinical impression is that hangxiety is more common in those that already have anxiety.

How can you prevent hangxiety?

For people for whom alcohol has a regular and/or severe negative effect on their mental health, it can be a good idea to take a step back and reassess their drinking habits.

The Centers for Disease Control and Prevention (CDC) notes that although around 90 percent of excessive drinkers aren’t expected to meet diagnostic criteria for alcohol use disorder (AUD), some signs of AUD include the inability to limit drinking and continuing to drink despite it causing professional or personal issues.

As the Alcohol and Drug Foundation (ADF) explains, reducing the amount of alcohol you consume is the best way to reduce your risk of hangxiety.

The World Health Organization notes that there is no amount of alcohol consumption that is safe for your health. To reduce harms associated with alcohol, the UK’s National Health Service recommends not drinking over 14 units per week, preferably all spread over three or more days (one shot of 40 percent ABV spirit = one unit). Australian guidelines suggest no more than four standard drinks a day, or 10 a week. The Dietary Guidelines for Americans recommends either not drinking at all or keeping it to two drinks a day for men and one drink a day for women.

But what can you do if the drinks (perhaps a couple too many) are already in your system, the anxiety is kicking in, and it’s too late to follow that advice?

It's suggested to avoid stimulants and, importantly, further alcohol consumption. Although taking in more alcohol can ease some symptoms, it can contribute to continuing dependence. “I see a lot of patients with hangxiety. Some people will try to ‘relieve’ the unpleasant symptoms of their drinking by drinking more but this can lead to more panic attacks, even seizures,” Dr Niall Campbell, a consultant at UK independent mental healthcare provider Priory, told their website.

The ADF recommends the classic hangover activities of resting, eating, and getting some hydration, alongside mindfulness, talking to a friend, and distracting yourself if you can. However, as the NIAAA explains on their website: “There is no way to speed up the brain’s recovery from alcohol use,” and you will probably just have to wait until the symptoms of the night before subside.

The content of this article is not intended to be a substitute for professional medical advice, diagnosis, or treatment. Always seek the advice of qualified health providers with questions you may have regarding medical conditions

All “explainer” articles are confirmed by fact checkers to be correct at time of publishing. Text, images, and links may be edited, removed, or added to at a later date to keep information current.