Sleepiness after sex
There are many popular answers on male sleepiness after sex, most of which focus on exertion and relaxation. Dr. Patti Britton (undated) on iVillage, S Thompson (2006) on AssociatedContent, and even the book 'Why Do Men Fall Asleep After Sex? (Leyner and Goldberg, 2006)*. However, scientific publications on the subject appear to be sparse. Brissette et al (1985) found no differences between sleep patterns after orgasm or two control conditions for either men or women.
scarletazalea points out Melinda Wenner's (2006) column "Why do guys get sleepy after sex?" which suggests the pituitary hormones prolactin, oxytocin, and vasopressin may be the key. Wenner references, for example, Brody and Kruger's (2006) findings that prolactin release is 4 times greater after intercourse than masturbation. However, while prolactin levels increase during sleep (Sassin et al, 1972), it hasn't been linked to increased sleepiness in healthy humans. Wenner suggests that prolactin-excreting tumors may cause sleepiness, but the National Institutes of Health do not list sleepiness as a symptom of prolactinomas. Heinrichs et al (2003) dosed subjects with oxytocin and no change in wakefulness was reported. Similarly, Snel et al (2003) did not find any change in wakefulness with vasopressin administration to male subjects.
Honestly, I think a more interesting question is "Why don't women get sleepy after sex?" I haven't observed additional sleepiness in men after morning sex. I also didn't find any studies demonstrating that men actually were sleepy after sex, or that women weren't. I'm not saying that this isn't the case, but I'd be extremely grateful to anyone who could find such a study.
*Bonus: read or listen: interview with Leyner and Goldberg, authors of Why Do Men Fall Asleep After Sex?, on their title topic. They blame the muscle mass.
scarletazalea points out Melinda Wenner's (2006) column "Why do guys get sleepy after sex?" which suggests the pituitary hormones prolactin, oxytocin, and vasopressin may be the key. Wenner references, for example, Brody and Kruger's (2006) findings that prolactin release is 4 times greater after intercourse than masturbation. However, while prolactin levels increase during sleep (Sassin et al, 1972), it hasn't been linked to increased sleepiness in healthy humans. Wenner suggests that prolactin-excreting tumors may cause sleepiness, but the National Institutes of Health do not list sleepiness as a symptom of prolactinomas. Heinrichs et al (2003) dosed subjects with oxytocin and no change in wakefulness was reported. Similarly, Snel et al (2003) did not find any change in wakefulness with vasopressin administration to male subjects.
Honestly, I think a more interesting question is "Why don't women get sleepy after sex?" I haven't observed additional sleepiness in men after morning sex. I also didn't find any studies demonstrating that men actually were sleepy after sex, or that women weren't. I'm not saying that this isn't the case, but I'd be extremely grateful to anyone who could find such a study.
*Bonus: read or listen: interview with Leyner and Goldberg, authors of Why Do Men Fall Asleep After Sex?, on their title topic. They blame the muscle mass.