Picture the scene: you’ve had blissful sex with your partner. You orgasmed (maybe more than once!) and are gearing up for some post-coital snuggling and talking about the day.
Then – tale as old as time – your partner falls asleep. What’s going on?
“Orgasm releases a whole cocktail of hormones and neurotransmitters that are known to enhance mood and reduce stress, both of which are conducive to sleep,” certified sex expert and founder of bedbible.com, Isabelle Uren, tells HuffPost UK.
One such hormone is called prolactin – and that’s often cited as a key player in falling asleep after sex, she explains.
“Not only does this hormone play a role in sleep, but it’s also linked to feeling sexually satiated and the refractory period, which inhibit further sexual activity in men,” says Uren.
So why do men drop off so quickly after sex?
While there aren’t many studies available specifically on why men tend to drop off so quickly after having sex, doctors Mark Leyner and Billy Goldberg – authors of the aptly-named book Why Do Men Fall Asleep After Sex? – suggest exertion during sex depletes the muscles of energy-producing glycogen.
And “since men have more muscle mass than women, men become more tired after sex,” they said.
The physician duo also explained how, after orgasm, the chemicals oxytocin, prolactin, gamma amino butyric acid (GABA) and endorphins all contribute to that “roll over and snore” feeling in both men and women.
“They seem to be secreted in equal amounts in men and women, but we all know who orgasms more frequently,” the pair wrote in their book.
They’re right – studies have shown how more than 90% of men usually experience orgasm during intercourse, compared to 50% of women.
It’s not just men who get sleepy
Although we tend to think it’s only men who are straight off to the land of nod after sex, there’s actually some evidence to show that women are more likely to.
A small study of university students found female participants were more inclined to fall after sex than male participants – with or without orgasm.
The study also found female participants whose partners had ejaculated inside them showed higher instances of falling asleep.
What if you don’t want to go to sleep?
Being intimate can make you want to spend more time together, having a laugh and catching up, especially if it’s been a while since you’ve last been together.
So how to combat that post-sex sleepiness? “You should also keep the lights on,” sleep expert Dr Christopher Winter told Men’s Health. “That way, you won’t kickstart your sleep cycle.
“Also, make sure you pick a sex position that’s not horizontal, Sure, it’s obvious, but lying on your back signals to your body that it’s time to sleep.
“And get out of bed once you’re finished. Over your lifetime, your brain has come to associate the bed as a location for dozing. It’ll be nearly impossible to fight the urge to hit the hay if you just lie there quietly. So no snuggling allowed!”