How does alcohol affect the brain?

It’s time for our question of the week, and Jack has been fermenting the facts of this question from Donald with the help of Joe Galea from the University of Birmingham.

Jack - We’ve all been there, one drink becomes two, two becomes four and then all of a sudden our volume goes up and our vision starts to blur. But why does alcohol cause this? Over to Joe Galea from the University of Birmingham, to distil the answer for us...

Joe - The compound in our alcoholic drinks that gets us drunk is ethanol, and it’s used across a wide range of industries as a combustible fuel. Therefore, it is not surprising that when we drink such a poisonous liquid in alcoholic drinks, it can have powerful and long-lasting negative side-effects on our brain. Once alcohol enters the bloodstream, it starts to affect how the brain functions by altering levels of neurotransmitters.

Neurotransmitters are essential chemical messengers which transmit messages between neurons. In other words, they allow brain regions to communicate with one another. Neurotransmitters can either be excitatory or inhibitory; therefore one brain region (or neuron) can increase or decrease another brain region’s activity through neurotransmitters. Crucially, alcohol increases the effects of the inhibitory neurotransmitter GABA, and reduces the effects of the excitatory neurotransmitter glutamate. As a result, it has a general suppressive effect on brain function which may not be surprising given alcohol is known as a depressant.  

Jack - But since GABA and glutamate are found across the entire brain, maybe alcohol does a lot more than just mess with movement. Back to Joe....

Joe - In fact, alcohol has a strong depressant effect on vision, hearing, touch and basic bodily functions. For example, drinking very large amounts can slow your heart rate and breathing down to dangerously low levels. However, alcohol does have a particularly strong effect on an area of the brain called the cerebellum, which is a small structure at the back of your brain important for movement and coordination. As the cerebellum has a high level of neurons which are controlled by GABA, alcohol causes the functioning of the cerebellum to be highly impaired. This leads to the standard ‘drunk’ characteristics of inaccurate movements and a lack of coordination. Long-term alcohol abuse can in effect poison the cerebellum and cause cerebellar ataxia - a chronic disease associated with a lack of movement control, which persists even if the person has given up drinking.

Therefore, even though alcohol influences the entire brain through its effects on neurotransmitters, the main characteristics associated with being ‘drunk’ are primarily due to alcohol’s impact on the cerebellum.  

Jack - Thank you Joe for your expertise.

We also had several spirited suggestions in the forum, this question sparking discussion by chiralSPO about GABA pathways as well as the difference between acute and chronic effects of alcohol, and from evan_au about how genetics could have a role.

Next time, we’re considering this question:

Chani - My socks never stay together in the wash. One always disappears. Is there a scientific explanation for where those socks go? Why are they so unhappy in monogamous relationships?