Though a little bit of alcohol does seem to make us fall asleep and enter deep sleep better, recent studies have shown that this only lasts for the first part of a full night’s sleep. In this study, participants were instructed to consume anywhere from one to six drinks thirty to sixty minutes before bed. Results showed that subjects who had more alcohol woke up more frequently and experienced lighter sleep during the second half of the night, even though they fell asleep faster than the other subjects. This was identified as a “rebound effect” where the alcohol had been metabolized and all the sleep variables from alcohol had been reversed. Interestingly enough, we still don’t know how the rebound effect is caused because sleep is still not fully understood.
According to the NY Times this is the mechanics behind being able to fall asleep quickly: “Alcohol mimics gamma-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the brain. When bound to a GABA receptor on a neuron, alcohol allows the influx of negative (or efflux of positive) ions, giving the cell a more negative charge. Thus, the neuron’s attempt to fire an action potential is thwarted. Alcohol also inhibits the brain’s major excitatory neurotransmitter, glutamate, by blocking function at glutamate’s NMDA receptors. Since glutamatergic and GABAergic neurons comprise 90% of all brain cells, this is a pretty big deal. Especially since alcohol also enhances GABA absorption back into the neuron, and even more especially since GABA is recycled into glutamate in a vicious cycle: After an evening of drinking, the theory is that GABA dominates the first half of the night, allowing us to fall asleep (and deeply!). But once GABA is metabolized, much of it becomes the excitatory glutamate. And it’s in glutamate-releasing brain regions (such as the reticular activating system which partially modulates sleep/wake and arousal) that the midnight disruptions kick in.” So for all the college party-goers out there, you probably shouldn’t be binge drinking at all…
- Alcohol, Sleep, and Why You Might Re-think that Nightcap (lions-talk-science.org)