Life Science

Why do guys get sleepy after sex?

-- asks J. from Brooklyn, NY.

September 25, 2006
The sated Satyr. [<em>Sleeping Satyr</em>, marble copy of bronze original, unknown sculptor c. 200 B.C.]
The sated Satyr. [Sleeping Satyr, marble copy of bronze original, unknown sculptor c. 200 B.C.]

For many women, the correlation between sex and snoring is one of those annoying facts of life: no matter when passionate encounters occur, men always seem to fall asleep immediately afterwards. Dave Zinczenko, the author of Men, Love and Sex: The Complete User Guide For Women, explained the phenomenon to Huffington Post writer Arianna Huffington this way: “Men go to sleep because women don’t turn into a pizza.”

I doubt I am ever going to become a pizza, and I’ll never have the foresight to order one beforehand. So in lieu of a cure, a better explanation will have to do. Although women sometimes feel sleepy after sex, the phenomenon does seem more pronounced in men. What is it, then, that spirals them into the land of nod?

First, the obvious reasons for sex’s somnolent sway: the act frequently takes place at night, in a bed, and is, after all, physically exhausting (often more so for the man than the woman, although this certainly varies). So when sex is over, it’s natural for a guy to feel sleepy.

Secondly, research using positron emission tomography (PET) scans has shown that in order for a person to reach orgasm, a primary requirement is to let go of “all fear and anxiety.” Doing so also tends to be relaxing and might explain the tendency to snooze.

Then there is the biochemistry of the orgasm itself. Research shows that during ejaculation, men release a cocktail of brain chemicals, including norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide (NO), and the hormone prolactin. The release of prolactin is linked to the feeling of sexual satisfaction, and it also mediates the “recovery time” that men are well aware of—the time a guy must wait before “giving it another go.” Studies have also shown that men deficient in prolactin have faster recovery times.

Prolactin levels are naturally higher during sleep, and animals injected with the chemical become tired immediately. This suggests a strong link between prolactin and sleep, so it’s likely that the hormone’s release during orgasm causes men to feel sleepy.

(Side note: prolactin also explains why men are sleepier after intercourse than after masturbation. For unknown reasons, intercourse orgasms release four times more prolactin than masturbatory orgasms, according to a recent study.)

Oxytocin and vasopressin, two other chemicals released during orgasm, are also associated with sleep. Their release frequently accompanies that of melatonin, the primary hormone that regulates our body clocks. Oxytocin is also thought to reduce stress levels, which again could lead to relaxation and sleepiness.

What about the evolutionary reasons for post-sex sleepiness? This is trickier to explain. Evolutionarily speaking, a man’s primary goal is to produce as many offspring as possible, and sleeping doesn’t exactly help in his quest. But perhaps since he cannot immediately run off with another woman anyway—damn that recovery time!—re-energizing himself via sleep may be the best use of his time.

And although there is conflicting information as to whether women feel sleepy after sex, a woman often falls asleep with the man anyway (or uses it for some key cuddling time), which is good news for him: it means she is not off finding another mate. When the man wakes up and she’s still there, he just might be ready to go again.

It’s also possible that sleepiness is just a “side effect” associated with a more evolutionarily important reason for the release of oxytocin and vasopressin. In addition to being associated with sleep, both chemicals are also intimately involved in what is called “pair bonding,” the social attachment human mates commonly share. The release of these brain chemicals during orgasm heightens feelings of bonding and trust between sexual partners, which may partially explain the link between sex and emotional attachment. This bond is favorable should the couple have a baby, as cooperative child rearing maximizes the young one’s chances for survival.

The bottom line is this: there are many potential biochemical and evolutionary reasons for post-sex sleepiness, some direct and some indirect—but no one has yet pinpointed the exact causes. One thing, however, is certain: we females better get used to it, because it doesn’t look likely to change anytime soon.

I will leave frustrated American women with one final thought: if you are upset at the ubiquity of the post-sex snoring phenomenon, remember that things could be a lot worse. A recent survey of 10,000 English men revealed that 48 percent actually fall asleep during sex.

Talk about coitus interruptus!

About the Author

Melinda Wenner

Melinda Wenner gave up a much higher salary, a BMW and a comfortable life in the British suburbs in order to write for Scienceline. She is willing to trade her knowledge of molecular biology (and perhaps her list of sources) for a well-poured pint of Carling. Contact her at



DrS says:

What a waste of space! Either make it scientific, or make it a joke, but not both. This was not scholarly, scientific, journalistic, or even coherent. In a recent study? What study? Published where? Just poor reading all around.

wonderful post, very informative. I’m wondering why the other experts of this sector do not understand this. You must continue your writing. I’m
sure, you have a great readers’ base already!

Ali says:

nice ………. very informative

Calm down. This is meant for the general public, if you want the specifics don’t search for what I know you searched for. Do a literature search on Google Scholar on get hits from NEJM and other journals. As for scientific and scholarly, it wasn’t. As for coherent, I thought it brought up some good information. I’m sure the studies exist. They probably just got dumped down in the continual cycle of people writing reviews of reviews.

sherri says:

I have had 5 partners in total.. i am now 31 and in all the years i spent being physical with them.. none of my bf’s have ever fallen alseep, nor have they stopped before at least 3 to 4 rounds. I lived with one bf for 5 years and we had sex a minimum of thrice a day. once 18 times in day… But he never fell alseep on me.. The weird thing is, if i wished to sleep, i could instantaneously. I do have insomnia and have for years, but sex is the only thing that gets me to sleep. I am yet to experience a partner falling asleep on me..

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This is exactly the 4th post, of your blog I really went through.
And yet I love this specific one, “Why do guys get sleepy after sex?

Michael says:

To clarify a few things.

a) It is the chemical release that causes fatigue immediately after ejaculation in men, it’s called Science, look it up peoples! This reduction can carry on for days for some people with low dopamine b) No, 48% of British men haven’t fallen asleep “during” sex, complete fabrication (I’m not even British) c) 38% of all commenter’s on this blog are really really stupid.

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Sam says:

Ill go with the chemical release explanation. Just know I cant help it!!!!

PHerz says:

Dave’s ‘blood pressure / heart rate’ theory. This is great example of why science requires empirical testing before a theory is formed and not just cursory rhetoric to prove hypothetical value to form a theory. If Dave’s ‘blood pressure’ theory were correct (from long time ago in 2008) wouldn’t people get sleepy anytime they raise their heart rate like after a jog, swing, gym, difficult job interview, etc? No people do not, in fact they generally get less sleepy after these activities, not even for a short period immediately after does an athlete get ‘sleepy’ by just raising their blood pressure. Give it a rest Dave and go back to neurochemistry causal chain like the author superbly did!

Airon says:

Easy there Richard, you don’t want to come across as brash, do you.


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James says:

women can have much longer lasting orgasms than men. in fact a women’s orgasm last 4 times longer in duration. not to mention women and girls can have multiple in a row, one after another. my girlfriend often has multiple, and she can have 5,10,15 in single session. I just have one, which lasts an average of 5 seconds. it’s like ah oh, yes, I’m done, than I have to wait a while. she on the only hand sometime has orgasms for 2-5 minutes, with all her orgasms combine, she is in heaven. us guys often get envious of this female capabilities. But than I think to myself and say, well I can pee standing up, and it’s the women that have to have periods every month, they are also the ones that have to be pregnant for 9 months, and give birth and endure labor pains. so I say it’s perfectly fair seeing they go through a lot more than us guys, it’s only right they are the ones to get more pleasure from sex.

Joshua says:

48% english men fall asleep during sex, what tripe! there wouldnt be any babies if that was the case, silly americans..

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Pia says:

Hahaha, I love the dude that wrote that men do all the work because women EXPECT them to do all the HUMPING and they themselves just lay there like dead fish! Sure, thatäs sad women that do that, BUT I have NEVER heard of a sexually mature women that says great sex involved lots of just HUMPING! Sure, I want my man to thrust, long and hard, quicker, lighter whatever, but to, like this dude, imagine that it´s either the man that “does all the work ny humping” or the women should start doing “the work” and get on top, is just a VERY sad idea of what great sex is all about! Not only is it something great couples to TOGETHER, also if one exists in the moment and that mpment is as pleasure filled as sex should be one doesn´t even have to THINK of what to do.

About the falling asleep factor, sure most men get tired after sex, but most men can also relax for a while and fous on staying awake if they feel like staying awake. It all DEPENDS! But one think that I DO think has sosmething to do with it is that men give up something, namely their semen, when they orgasm nd women achieve something, namely the same. hence the man gets tired while the women rather gets energized. Another thing I don´t understand in this thread is how many of you that say most people have sex in the evning/night time. I don´t find that to be particularlu true, but who cares? I also don´t understand why women would be upset when and if the man falls aslepp- if the sex is good, the relationship is good etc then it´s all fine regardless. A women that gets upset at that has truly other issues with the man at hand.

tigger says:

i think it is because he is just tired from all of that emmotion of the fact that we just had sex for the first time. oh yeah and guess what ladys i am pregnat with a boy!

tigger says:

any guys wanna have sex? cause my boyfriend dumped me.And im also pregnet guys!

tigger says:

yes mirmo and yes michael he is ignorant

Doug Schap says:

I always thought:
We loose a bunch of energy because because the sperm cells need a lot of energy to swim around

Queen Wilson says:

Omg if I could sebd u a pic lmao I am called knock out (was before marriage tehe) but my husband passes out immediately I mean immediately lol I have always done this to guys n I couldn’t for the life of me figure it out thank so much for the info lol I will share this woth hom when he wakes up lol ps I play call of duty or black ops when we are done the deed lol no snuggle time for me lol ok sometimes. God bless

Queen Wilson says:

Pardon my grammar

Queen Wilson says:

Oh yea Teddy Pendergrass song love tko cracks me up lol I think he better let it go looks like another love tko

tigger says:

thats one reason for sure Doug Schap

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robert says:

Because women make us wait all freakin day long and then we are tired much too tired to couple.

robert says:

Because women make us wait all freakin day long and then we are tired much too tired to be coudle

Martin says:

Firstly.. this post is over 7 years old. People are still commenting on it.
And thusly, I wanted to know why men are so exhausted after sex, google led me to this post. I don’t feel tired at all after sex, although my recovery time is roughly 4-6 hours. I remember when I was younger 17-30ish I was rampant, my recovery was in minutes, not hours.

These days now 44, I would not call myself physically unfit, but not as strong as I once was, I am absolutely exhausted after sex with my wife, whom I’ve been married to for over 14 years.

Which carries to another comment later in the post. 6 months to 2 years. The good stuff.. is not commitment.. it is honour. To leave my wife without a cohesive argument for doing so, is dishonourable. My honour, makes me commited.

And lastly, it is claimed that my southern brethern fall asleep 48% of the time during sex.. I wonder (from my own experience) if this is only whilst having sex with american women ;)

Michael says:

It is possible that because prolactin counteracts dopamine and dopamine is a key chemical in arousal, that more prolactin in released after intercorse than masterbation because arousal levels are higher in intercorse, so more dopamine, so more prolactin?

Ah, Martin, you witty man. Actually, fantastic comments from everyone. My favourties: 13, 14, 23, 50, (and then I stopped reading…)

Different Strokes says:

Excellent article. I just found this article this morning after being extrodinarily tired after making love to my wife last night, we’re TTC.

I am a 33 year old male, relatively fit and regularly excercise. I have been married for 3 years.

Back when i was single I could go 4/5 times a night with a girl if I knew it was just a one night stand. I’d fall asleep but wake up fairly soon and get back on the job. I’d say my recovery was 30 minutes if that.

However in a long term loving relationship it’s just completely different. I am wholly satisfied after making love to my wife and I have absolutely nil desire to try again anytime soon!

I also get incredibly tired, I am still a bit tired almost 14 hours after the deed even though I had plenty of sleep (8hrs+)

It’s good to understand that there’s a bio chemical reason for this behaviour. Even when we don’t make love last thing at night, I’ve been known to fall asleep for 2/3 hours.

Again this only happens with my wife.


Warren G Wonka says:

If you read “Sex at Dawn”, they hypothesize that in our primordial hunter-gatherer clans, personal ownership of anything was unthinkable. Everything was shared. After sex, the single-ejaculation men fell asleep; the multi=orgasmic women emitted coital cries that attracted the attention of any of their friends who were feeling frisky.

As a participant a few times with a lady who was “pulling a train” at a swing club, I can testify there is quite a feeling of comradery with the other lads in line and surrounding the lady. If you feel secure that you will get your turn, everybody is your friend.

Aside from that, the human penis is a tool admirably formed to remove previously deposited semen. Other animals do not have our coronal ridge. Male gorillas are twice the physical size of their females. The human genetic competition takes place within the woman’s reproductive tract rather than between physically competing males. The various spurts of an ejaculation have differing chemical composition in order to promote the current occupant’s chances of conception and inhibit previous and following deposits.

Charles Wycoff says:

Sperm Cells and blood cells can be thought of as coming from the same ‘stock pile’.Overly simplified, consider the ‘full amount’ of ‘source material’ to make one cc or one ml of blood. It take 40 times that to make one cc or ml of sperm. Volumn of sperm per man varies for many reasons. Lets say it averages 3.5 ccs per ejaculate. This is equivilant to losing 140 cc’s of blood. The body doesn’t ‘order out’ for the material that makes one cell bringing life to a human being. There can be little hope of success by ‘planting’ one red blood cell into an ovum and getting a whole human being.

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wileyrin says:

Glad this has been explored. I was thinking about this and propose another angle perhaps not mentioned yet. Besides the scientific/physiological reasons I believe that there is one that may further why nature/God has provided this phenomenon. In more primitive times men were the protectors of the family/clan/tribe. If after sex both male and female fell asleep, then the sleeping couple would be vulerable to attack by enemies either animal or human. By natural physiological engineering and differetiation of male & female reactions after sex it left one of the partners alert to be able to protect the family while the other slept. The woman was then able to take the role as guardian of the family since she was not immediately taken over by the desire to sleep. Such protective roles are not so important today unless such emergencies as a fire might occur. Still it’s an interesting thought to entertain how perfectly we have been designed from the beginning of time.

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mnb says:

Not just sleepiness. Though I have never heard or seen much correlative confirmation (I’m rather constantly seeing promotion of the opposite), it is also utterly destructive of any concentration and mental and physical tension and capability. It’s not completely predictable, and it depends on other factors, like the stress level that is created by the lack of this release, but most importantly the possibility to relax afterwards (so not having requirements anyway). Maybe I’m just strange this way, but this has always been a serious problem for me, since puberty.

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