There's no more clichéd excuse to skip sex than the old line: "Not tonight, honey; I've got a headache." In fact, though, if the headache is genuine, sex might be just what the doctor ordered, according to a Vancouver sexologist.

"Having sex actually decreases headaches," Ashleigh Turner says in a phone interview. "It could be one of the best things you could do."

Relief from a pounding headache is just one of the health benefits of sex—benefits that are all too often overlooked, in Turner's view.

"A lot of times with sex, we focus on the negatives—things like the dangers and all the scary stuff—and we rarely take the opportunity to focus on the positive."

Headaches and other types of pain can be relieved during sex because it triggers the release of the hormone oxytocin. In a study published last year in the Bulletin of Experimental Biology and Medicine, 48 volunteers who inhaled oxytocin vapour and then had their fingers pricked reported pain sensitivity reduced by more than half.

"Orgasm is really great for menstrual cramps," Turner adds, saying it reduces the intense discomfort so many women experience.

The release of oxytocin, which is also known as the "love hormone", helps build intimacy. A 2005 study published in Biological Psychology evaluated premenopausal women before and after physical contact ending with hugs from their husbands and partners. Researchers found that the more contact, the higher the oxytocin levels.

"Oxytocin is considered the bonding chemical when women give birth, and after sex the same types of feelings are released," Turner says.

"This all goes back to a holistic view of health: sex allows for deep human connection, positive, pleasurable feelings, and oxytocin release, so it really does increase the feel-good feelings in the body."

The oxytocin released during orgasm also seems to promote better sleep. "A lot of people find that once they've had sex they can relax and actually go to sleep," Turner says.

Another positive is that sex is a stress reliever. According to a study that appeared in Biological Psychology in 2006—which measured participants' blood pressure in response to stressful situations, like speaking in public—people who had had intercourse beforehand had lower blood pressure and reduced stress levels than did those who had other forms of sex or none at all.

There's also an argument to be made that sex is a form of exercise, Turner points out.

"There's a lot of different information on what exactly the caloric burn would be, but most commonly stated is that about half an hour of sex burns between 85 and 200 calories," Turner says. Put that way, when combined with exercise like cardiovascular workouts and strengthening routines, sex could be considered another form of cross-training.

Sex plays a role in improving cardiovascular health. In 2002, the Journal of Epidemiology and Community Health published a study showing that researchers found having sex twice a week or more reduced the risk of fatal heart attack by half compared to having sex less than once a month. That same study found that frequent sexual intercourse is not likely to result in a substantial increase in risk of strokes in middle-aged men.

There are other health benefits of sex specific to men. A 2004 study published in the Journal of the American Medical Association found that frequent ejaculations—21 or more a month—were linked to lower prostate-cancer risk in older men, compared with less frequent ejaculations of four to seven monthly.

For women, sex can help strengthen pelvic-floor muscles. That helps reduce the risk of incontinence that accompanies aging. "Regular, positive sexual activity keeps muscle strength and tone up," Turner says. "It's good for the internal vaginal muscles and for bladder health. It helps maintain vaginal health by helping with lubrication."