Describe alcohol's effect on sleep architecture.

• A. Alcohol facilitates sleep onset but fragments sleep, decreasing REM and slow-wave sleep, and increasing awakenings in the second half of the night
• B. Alcohol has no effect on sleep architecture
• C. Alcohol improves REM sleep and deep sleep
• D. Alcohol only affects sleep if consumed in the morning

Answer: (A)

Alcohol has a biphasic effect on sleep. At the start of the night it acts as a sedative, helping you fall asleep more quickly by increasing GABAergic inhibition, which reduces wakefulness and shortens time to sleep onset. But as the body metabolizes the alcohol, sleep becomes more disrupted. Deep sleep (slow-wave sleep) and REM sleep are reduced, making the first part of the night less restorative. As blood alcohol concentration falls, arousal returns and sleep becomes fragmented, with more awakenings in the latter half of the night. REM sleep may be particularly reduced early on and can show rebound later, often with more awakenings or vivid dreams. In short, alcohol helps you drift off but worsens overall sleep quality by reducing key restorative stages and increasing interruptions later in the night.