I deal with alcohol and how it affects sleep in Alcohol Explained, but I think it is worth going in to a bit more detail on exactly how drinking alcohol impacts our sleep. To appreciate the effect fully we need to understand three things; how our brain works, how alcohol affects it, and sleep.
The first two parts we need to understand (how our brain works and how alcohol affects it) is dealt with in detail in Chapter 2 of Alcohol Explained (which you can read here). However it is probably worth a quick recap.
The human brain contains and manufactures its own supply of drugs, hormones and chemicals that it excretes in exactly the right amounts and in exactly the right quantities to keep us alive and well. Human knowledge of this is extremely limited at the present time. We do not have a complete list of all these drugs, hormones and chemicals, still less do we understand the delicate interplay between them and how they balance and interact with one another. Fortunately we don’t need to understand the full complicated interaction, we just need to appreciate that there is a delicate chemical balance going on in our brains. What it is working well, we feel positive, confident and mentally resilient. This is not to say we don’t encounter problems, but generally speaking we feel able to cope with all but the most serious of these problems. A key point to understand is that the brain works to maintain this delicate balance.
Whilst we do not yet have a complete list of these naturally occurring drugs, hormones and chemicals, it is helpful for the purposes of this article to put them into 2 main categories; stimulants and depressants. Stimulants at the things that wake us up, increase our heart rate, and make us feel more alert. An example of this would be adrenaline. Depressants on the other hand are things that calm us down and make us feel relaxed. Although this is a vast oversimplification of all the different drugs, chemicals and hormones that the brain creates and secretes, in fact many of these do fit quite nicely into one of these two categories.
Alcohol of course is a very powerful depressant, and by this I mean it is something that decreases or inhibits nerve activity. This is why drinking makes us feel relaxed and uncoordinated. The problem is of course that the brain then seeks to counter the depressing effects of the alcohol by releasing more stimulants. The alcohol then wears off leaving the excess stimulants. This is why people often find that the day after drinking they feel anxious and even shaky. The process is best visualised in the chart below:
What you can see here is firstly your brain as it is naturally (with small amounts of both stimulants and depressants which balance each other), then the increase in depressants as the alcohol enters our system, then the increase in stimulants as the brain seeks to counter the depressive effects of the alcohol and restore the internal balance, then the alcohol wearing off leaving only the excess stimulants. Essentially what is going on is that alcohol (being a depressant) upsets the delicate balance of the brain, and the brain seeks to re-establish that balance. The brain seeks to redress the balance by secreting more stimulants. However when the alcohol wears off only the stimulants remain.
So now we’ve dealt with the first of the two things we need to deal with; how our brain works and how alcohol affects us. Now let’s look at sleep.
As with our understanding of the human brain, our understanding of ‘sleep’ in in its infancy. There is much we as human beings do not understand about sleep, but again fortunately to understand how alcohol affects sleep we only need to understand the basics which are this; we sleep in different cycles, and one of the main differentiating factors of these cycles is how deeply asleep we are. One of the cycles of sleep is REM (Rapid Eye Movement) sleep. REM sleep is categorised by rapid movement of the eyes, increased heart rate, and parts of the brain show activity similar to if you were awake. It is closely associated with dreaming. Essentially it is a period of sleep in which you are raised up from deep sleep into a state that is very close to being awake. No one actually knows what the purpose of REM sleep is, but what we do know is that is essential. In tests, rats that have been deprived of REM sleep die within 4 to 6 weeks.
So now we’ve got the basics in place; how our brains work, how alcohol affects us, and sleep. So what happens when we put them all together?
When you drink and then go to sleep, the depressant effects of the alcohol holds sway. You can’t get into REM sleep because that arena of sleep requires you to be very close to waking; your brain needs to raise you up to just below the level of being awake. Being drugged on alcohol your brain struggles to raise you to this level, so for the first 4 or 5 hours your brain finds it extremely difficult to put you into the REM sleep cycle. You either have no REM sleep, or far less (and far worse quality) than you ought to have.
After this 4 or 5 hour period the alcohol has usually worn off to such an extent that the residual stimulants now outweigh the depressants and the effect of this is that it is generally impossible to get to sleep at all. This is why so many people find that after drinking they wake in the early hours of the morning completely unable to get back to sleep. Even if they do manage to sleep it is usually fitful and spasmodic. They can be absolutely exhausted, their bodies crying out for sleep, but they will be unable to sleep because the effect of the residual simulants leaves them totally unable to sleep. It’s like trying to sleep after a few jugs of very strong coffee.
This is why, after drinking, you can be in bed for 8 10 or 12 hours, and still end up starting the day tired and drained. It is also worth bearing in mind that even just one or two drinks is enough to upset the delicate chemical balance of the brain and will lead to disturbed sleep.