Although it may seem like a nightcap can help you sleep, a recent review of studies analyzing the effect of alcohol on sleep has identified how it can keep you from sleeping well.
Alcohol does help you fall asleep faster
This is why people sometimes use alcohol as a sleep aid. But while alcohol consolidates the first half of your sleep cycle, it causes disruption in the second half.
Alcohol increases slow-wave sleep in the first half of the night
Slow-wave sleep, or deep sleep, usually comprises stage 3 and 4 of non-REM sleep. During deep sleep, the body repairs and regenerates tissue, builds bones and muscle and strengthens the immune system. While this is good, increased deep sleep can cause other problems, such as sleep walking and sleep apnea.
The more alcohol you consume, the more it affects your first half of sleep
Low-to-moderate drinking doesn’t appear to have consistent effects on REM sleep in the first half of the night, but high doses appear to reduce REM sleep significantly. Lack of REM sleep can have negative effects on concentration, motor skills and memory.
Alcohol significantly delays the first REM sleep cycle
Drinking any alcohol can significantly delay the onset of the first REM sleep cycle, which makes sleep less restful, and could be connected with depression. In addition, alcohol reduces the total amount of REM sleep at night.