The answer comes from Melinda Wenner of the New York University Science Project, Health and Environmental Reporting Program.
For many women, the connection between sex and snoring is one of those annoying facts of life, because men always seem to fall asleep right after.
Although women sometimes feel drowsy after sex, this phenomenon is more pronounced in men.
And since there is no cure for men falling asleep after sex, a convincing explanation for the matter may satisfy women.
Firstly:
The obvious reasons why sex has the same effect as taking a drug is that sex often takes place at night in bed and the process is physically demanding (more for men than for women).
So when sex ends, it is natural for a man to feel sleepy due to all these causes.
secondly:
In research, a survey using positron emission tomography (PET) showed that in order for a person to reach the stage of sexual arousal, he must first put aside all his fears and anxieties.
And to do so also tends to be relaxed, which explains the reason for the tendency to sleep.
Furthermore, there is a chemistry to the occurrence of sexual arousal itself.
Research has shown that during ejaculation, men release a cocktail of chemicals or hormones from the brain, including norepinephrine, serotonin, oxytocin, vasopressin, nitric oxide (NO), and prolactin.
The secretion of prolactin is responsible for the sensation of sexual satisfaction, the stage that mediates the "recovery time" at which men realize they must wait before beginning a new cycle of intercourse.
And studies have shown that men who have a deficiency in the secretion of the hormone prolactin pass the time of resuscitation at a faster pace.
Levels of the hormone prolactin are naturally higher during sleep, and animals injected with this substance became instantly tired.
These suggestions formed a strong link between the prolactin hormone and sleep, and therefore it is likely that the secretion of the hormone during sexual arousal causes a feeling of sleepiness later in men.
Side note:
The prolactin hormone also explains why men sleep more after intercourse than during masturbation.
For unknown reasons, prolactin is released four times more during sexual intercourse than it is during masturbation, according to a recent study.
Oxytocin and Vasopressi, hormones that are also released during sexual arousal, are also linked to sleep.
And their secretion always accompanies the secretion of melatonin, a primary hormone that regulates the biological clock in the body.
Oxytocin is also believed to reduce tension and stress, which leads to a state of relaxation and drowsiness.
But what about the evolutionary causes of post-sex sleepiness?
This is a more difficult question as it seems to explain.
Talking about the reasons According to evolution, man has a primary goal, which is to produce the largest possible number of offspring, and as we can see, sleep does not help at all in pursuit of this goal.
But perhaps because he can't immediately have sex with another woman anyway because he's in the re-refreshing phase, sleep is the best way to get through this phase.
It's also possible that sleep is just a "side effect" related to more important evolutionary causes of oxytocin and vasopressin secretion.
In addition to being linked to sleep, the two substances are closely related, implicit in what is called the "double bond," the social attachment shared by human partners.
The secretion of these brain hormones during sexual arousal raises the sense of bonding and trust between the two parties during sex.
Which partly explains the link between sex and emotional attachment.
And the preferred bond is the attachment of the spouses through a child, and the opportunity to raise a child increases the cooperation between the young spouses and increases the chances of their continuity together.
Conclusion:
There are many biochemical actives and evolutionary causes of falling asleep after sex, some direct and some indirect, but no one has yet identified a definitive cause.
And a recent survey of 10,000 English men revealed that 48% actually fall asleep during sex.