Matt Soniak
Why Does Sex Make Men Sleepy?
by Matt Soniak - June 1, 2010 - 3:17 PM

Alfred Kinsey, biologist, pioneering sex researcher and founder of the Institute for Sex Research at Indiana University*, once wrote that “a marked quiescence of the total body is the most widely recognized outcome of orgasm,” more noticeably among males. Why is that?

Let’s get the obvious reasons out of the way first. Sex often, though not always, happens at night in a bed and is physically exhausting. If you’re tired to begin with, all that physical exertion only adds to it, and since you’re already in bed, it’s only natural to be sleepy. Compounding this is the fact that sex dominates your attention when you’re having it (and sometimes when you’re not), so you don’t pay attention to your breathing and wind up breathing shallowly and holding your breath pretty often. These aren’t really the sorts of things you want to do during vigorous exercise, as they lead to oxygen deprivation and—all together now—sleepiness.

There’s also the biochemistry of the orgasm to consider. After sex, a man’s brain releases a slew of hormones and neurotransmitters. Some of them, like prolactin, oxytocin and vasopressin, have been linked to sleep as well as sex. Prolactin plays a role in sexual satisfaction by counteracting the effects of dopamine** (which is responsible for sexual arousal). It’s also been shown that the artificial delaying of an REM sleep period disrupts the rhythm of prolactin release, and that REM sleep is reduced in mice with prolactin deficiencies. Oxytocin and vasopressin have also both been implicated in the body’s regulation of sleep cycles. While none of these chemicals are fully understood and their links to sleep aren’t concrete, the circumstantial evidence suggests that they may play a part in pulling you off to a post-coital snooze.

What About the Ladies?

The phenomena of men falling asleep soon after sex is a little more well established than women doing the same—at least in that people notice it enough to make jokes about it on sitcoms, and write in to mental_floss asking about it. While I haven’t been able to find any science-backed evidence that post-sex sleepiness definitively affects men more than women, there are a few hypotheses floating around as to why it seems that way. In their 2006 book Why Do Men Fall Asleep After Sex?, Mark Leyner and Billy Goldberg, M.D. suggest that exertion during sex depletes the muscles of energy-producing glycogen. Because men usually have more muscle mass, they get more tired. And it’s entirely possible that women get just as sleepy, just as fast as men do after orgasm, but women simply have orgasms during sex less often than men do.

*Kinsey left his mark on a different field earlier in his career: entomology. He did his doctoral thesis on gall wasps and researched and published papers about them at the American Museum of Natural History in New York. Of the 18 million+ insects in the museum’s collections, about 5 million are gall wasps that Kinsey collected. In return for his collection, Kinsey received $400 and a lifetime membership to the Museum.

**The hormone may also mediate the “sexual refractory period,” or the recovery phase after an orgasm during which a man cannot have additional orgasms or achieve an erection.

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Comments (12)

  1. I totally don’t believe there’s a disparity here. In fact, this is one of my favorite insomnia cures.

    posted by myabsurdlife on 6-1-2010 at 3:34 pm

  2. In almost all cases of sex involving men, sex is over when a man has an orgasm, so a man falls asleep right after sex. Since only about 20% of women can have an orgasm from vaginal intercourse alone, of course we don’t experience the same sleep inducing benefits from sex as men do. If cuddling post-coitus is as much a problem for menfolk as sitcoms make it out to be, maybe you should work a little harder to make sure we get to finish off as well. Then, we’ll roll over and fall asleep to, easy peasy.

    posted by Lucy on 6-1-2010 at 3:51 pm

  3. I find that I am more sleepy than my fiance. He actually is more wired after sex than I am. Usually I can’t even get into cuddle-mode because I’m sawing logs. This happens to me whether I have an orgasm or not. I was hoping I would have more of an answer of why I am more sleepy in this article. Oh well I guess I’ll some research to do.

    posted by Colene on 6-1-2010 at 5:09 pm

  4. Interesting! I was expecting more of an anthropological explanation, like back in the caveman days men would finish off an exhausting day of hunting and running from saber-toothed tigers with a good romp to ensure the continuation of the species or something.

    posted by BorgQueen on 6-1-2010 at 5:36 pm

  5. My husband is up for hours after sex. I am passed out immediately after. It’s bizarre.

    posted by Amanda on 6-1-2010 at 6:57 pm

  6. I’m glad I’m not the only woman who falls asleep right afterward! My fiance jokes with me about this. I always get sleepy after sex, whether I orgasm or not! My fiance, though, will be energized and up for hours…he’s always ready to go out and do something and I’m the one who wants to sleep. Weird.

    posted by Rebecca on 6-2-2010 at 8:24 am

  7. Personally, I think the most logical reason would be that men generally work harder during sex and, thus, it tires us out. This is, of course, a general theory. Sure, there are cases where the woman is working as hard, or even harder (pardon the sexual puns) than the man. But in general, I think men work harder in the sack.

    posted by Ian from Baltimore on 6-2-2010 at 9:18 am

  8. I’ve always said that there is truth in comedy. Check out a few routines on XM/Sirius Raw Dog (150) and you will get a notebook full of sociological insights. I think Kinsey would have agreed. Comedians are willing to say things about the human condition others wouldn’t dare. And apparently, men seem to fall asleep more quickly than women aften knockin boots. Just sayin’

    posted by Dan on 6-2-2010 at 4:03 pm

  9. post-orgasm = sleepy

    when i have sex with someone who orgasms and then falls asleep and i haven’t orgasmed, i then lie there awake for awhile. however, when i have an orgasm as well, i’m asleep practically immediately.

    posted by Sonia on 6-2-2010 at 5:08 pm

  10. If you don’t want a nap after sex, you didn’t do it right.

    posted by demanding_little_witch on 6-6-2010 at 3:55 pm

  11. Yeah, it’s a pretty known thing that orgasm makes you tired. It’s not necessarily the sex it’s the chemicals released in the brain… Actually I’ve had more than one psych teacher tell us that if we’re having sleeping problems to have sex or masturbate before bed! Lol

    posted by tess on 6-6-2010 at 11:40 pm

  12. It’s male instinctual want to sleep alone. Cuddling afterward in modern times has no downfalls though, as it is accepted as normal.

    posted by Anonymous on 8-7-2011 at 1:19 pm

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