Believe it or not, sex and insomnia are closely linked.
Sleep deprivation and chronic insomnia can affect sex drive and even sexual function.
According to an article in The Chosun Ilbo, sex can even be a good natural insomnia remedy - but only for men.
The theory goes that sex increases levels of the hormone prolactin in men, which can promote sleepiness.
The article reports that for women, sex can encourage sleep - but it can also end up keeping them awake.
After doing a bit more research, I found that excessive levels of prolactin are associated with sleep and that prolactin levels peak during REM sleep and early in the morning - so there is some level of association here.
That being said, it seems unlikely that the higher levels that are naturally released after sex would be high enough to magically cure insomnia.
No doubt many men will be keen supporters of the theory, though!