By Claire Rostron:
Alcohol: why do we drink it? People have been consuming alcohol for at least 10,000 years. And when drinking water was rather risky, alcohol seemed a much safer bet. Amaldus of Villanova, a 14th-century monk, even wrote that alcohol “prolongs life, clears away ill humours, revives the heart and maintains youth”.
Today people will give you many reasons for their decision to drink and most of these reflect the effects it has on the mind and brain. But before you get too sozzled, one thing is for sure; it is certainly not a safer, healthier bet than water.
It depends on what you are drinking (some drinks like alcopops contain more sugar) and people obviously have different taste preferences. The fact that ethanol is created from sugars is also likely to increase our propensity to drink. For example, research suggests that some individuals have a predisposition to prefer sugar and this can make them more prone to developing alcohol addiction. Alcohol also seems to act on some of the same brain areas activated by sweet tastes.
Yet ethanol is not always perceived as pleasant; it can be quite bitter. If ethanol is given over time, rats show increasing “tasty” responses in their mouth and facial expressions. However, if it’s given after naltrexone, a substance that reduces opioid activity – which signals “liking” something among other things – in the brain, “aversive” reactions increase, and less alcohol is consumed. This suggests that the opioid receptors mediate how much we like alcohol. And substances like naltrexone are used to treat people with alcohol use disorder.
Dopamine, a neurotransmitter involved in controlling reward and pleasure in the brain, plays a key role in motivated behaviour and is also associated with many forms of addiction. Ethanol, like all other known addictive substances, increases the release of dopamine. This can cause you to drink more – why you might want a second, or a third drink, after the first one.
However, after repeated experience with addictive substances like alcohol, dopamine connections can remodel themselves, sometimes decreasing the numbers of receptors that bind dopamine. The size of this reduction is associated with a higher risk of relapse in alcohol addiction.
Drinking alcohol can be a form of “self-medication” used to unwind from workplace stress or ease study pressures, making it less “aqua vitae” (water of life) and more “aqua ad vitae” (water to counteract life). And more than 2,600 years ago, the Greek poet Alceus suggested, “We must not let our spirits give way to grief… Best of all defences is to mix plenty of wine and drink it”.
Stress is biologically mediated by the hypothalamic pituitary adrenal axis – a feedback system between the brain and the pituitary and adrenal glands. But acute alcohol consumption can stimulate this, increasing the production of several stress hormones including corticosterone and corticotropin. But the “stress” response also interacts with the reward effects from the dopamine system, so it may very well feel good.
Alcohol is known to reduce inhibitory control in the prefrontal cortex – the part of the brain associated with decision-making and social behaviour – coming more under the control of midbrain dopamine neurons. This leads to the loss of self-restraint that people report when drinking.
One noticeable effect, after just a few drinks, is an increase in sociability. But the loss of inhibition probably also underlies risk-taking behaviour while under the influence and goes some way towards explaining the association between drinking and accidents and injuries.
Despite the fact that we may opt to partake in a nightcap, research shows that certain doses of alcohol may reduce the amount of slow-wave and REM (Rapid Eye Movement) sleep we have. So it may help us to drop off faster, but alcohol doesn’t result in a better quality of sleep. REM sleep is important for cognitive processes such as memory consolidation, so reducing the time in which this process occurs has a detrimental effect on memory. Consolidation of emotional memories may be particularly affected.
It is also known that alcohol acts on the process of long-term potentiation – the way in which neurons remodel the connections between them after learning. So alterations in both REM and slow-wave sleep after drinking may potentially disrupt the brain’s memory processes.
This known effect has been used to support alcohol’s consumption throughout history: consume it and you can successfully dull your perception of pain. Pain-causing signals are detected by sensory neurons (or nociceptors) that pass this information through chemicals such as glutamate, via synapses in the spinal cord, up into the brain. But this ascending signal can be “dampened down” by alcohol, which is how it achieves some of its pain-dulling effects.
Unfortunately, research suggests that this pain dampening effect is highly variable. And while some people do consume alcohol to help relieve chronic pain, it is possible for tolerance to occur such that pain relief lessens over time. Enhanced pain sensitivity may even happen in chronic drinkers.
Not quite. While alcohol can make you feel warm temporarily, this is a perception generated by heat sensitive neurons (thermoreceptors) located in your skin that detect a rise in your skin temperature from an increase in blood flow in the vessels close to the skin’s surface. In fact, alcohol actually lowers your core body temperature because the rush of blood to the skin’s surface is a means of body cooling.
So while you may feel warm on the outside, you are getting cold on the inside. Alcohol consumption has also been shown to reduce the perception of cold air temperatures but it is thought that this effect may not come from changes in the dilation of blood vessels but may originate in the brain itself.
All in all, alcohol has multiple effects on your mind and brain. If you do decide to have a drink, for whatever reason, do so knowledgeably.
This article was originally published on The Conversation.
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