A tipple before bedtime may get you off to sleep faster but it can disrupt your night's slumber, say researchers who have reviewed the evidence.
The London Sleep Centre team says studies show alcohol upsets our normal sleep cycles.
While it cuts the time it takes to first nod off and sends us into a deep sleep, it also robs us of one of our most satisfying types of sleep, where dreams occur.
Used too often, it can cause insomnia.
Many advocate a nightcap - nursing homes and hospital wards have even been known to serve alcohol - but Dr Irshaad Ebrahim and his team advise against it.
Dr Ebrahim, medical director at the London Sleep Centre and co-author of the latest review, published in the journal Alcoholism: Clinical & Experimental Research, said: "We should be very cautious about drinking on a regular basis.
Alcohol reduces how much time we spend in rapid eye movement (REM) sleep - the stage of sleep where dreams generally occur.
As a consequence, the sleep may feel less restful, said Dr Ebrahim.
Chris Idzikowski, director of the Edinburgh Sleep Centre, said: "Alcohol on the whole is not useful for improving a whole night's sleep. Sleep may be deeper to start with, but then becomes disrupted. Additionally, that deeper sleep will probably promote snoring and poorer breathing. So, one shouldn't expect better sleep with alcohol."
The Sleep Council said: "Don't over-indulge. Too much food or alcohol, especially late at night, just before bedtime, can play havoc with sleep patterns.
"Alcohol may help you fall asleep initially, but will interrupt your sleep later on in the night. Plus you may wake dehydrated and needing the loo."