Sex and headache are inextricably linked by the age-old excuse: "Not tonight, dear. I have a headache."
But brain science is finding that it's more complicated than that. For many people, sex can turn a dull, throbbing pain into a raging headache. For a few who jump into bed feeling fine, orgasm can trigger a sudden headache. And for a minority of people, headaches are cured by a roll in the hay.
Now a small pilot study exploring the link between migraines and libido suggests there might be a reward for headache pain. In the June edition of the journal Headache, researchers found that young adults with migraines reported higher levels of sexual desire.
Dr. Timothy Houle, professor of anesthesiology at Wake Forest University School of Medicine in North Carolina and lead author of the study, wanted to see whether migraine sufferers thought about sex more than tension headache sufferers did.
Researchers looked at 68 college students, about half of whom were migraine sufferers; the other half suffered from the more typical tension headaches. He gave the two groups questionnaires, asking about their perceived level of sexual desire and inquiring into how much they think about having sex.
"Migraine sufferers reported higher levels of sexual desire by about 20 percent," Houle says.
What surprised him is that in an age group understood to delight in sexual awakening, they know they have even more carnal thoughts than their peers.
"Not only did migrainers rate their levels of desire higher, they were aware of the fact that their levels were higher," Houle says.
He wanted to study the possible link between libido and migraines because he knew that migraine sufferers have lower levels of the brain chemical serotonin than the general population. The chemical, associated with sexual desire, also responds to certain antidepressants. Those drugs, called selective serotonin reuptake inhibitors, increase the amount of serotonin available in the brain -- and often have sexual side effects including reduced libido.
Knowing from antidepressant research that sexual desire can be manipulated by serotonin levels, researchers reasoned that if heightened levels of serotonin can decrease libido, maybe low levels increase it.
The study has its skeptics.
"That's not my experience," says Dr. David Kudrow, neurologist at the California Medical Clinic for Headache in Santa Monica. "In general, people with migraines don't want to engage in anything, including sex. It just makes it worse." Even routine movements, such as walking up stairs, can increase the pain.
Although Kudrow's patients are typical, there is a wide-ranging and seemingly contradictory body of research on the connection between headaches and sex, orgasm and desire.
Some people have what's called coital cephalalgia, starting with a dull ache in the head and neck in the foreplay stage and getting worse during sexual activity, says Dr. Randolph Evans, professor of neurology at Baylor College of Medicine in Houston. Though causes aren't known for sure, muscle contractions or a temporary increase in pressure within the brain could lead to some headaches.
Still others have orgasmic headaches, or sudden severe headaches at the moment of orgasm. Experts speculate that the release of brain chemicals such as serotonin may constrict blood flow. For those people, researchers have found, calling it quits before orgasm can result in a headache lasting up to two hours. If they reach orgasm, the headache can linger two days.
It's important to take the first severe sex headache seriously. Sexual activity is the forerunner in up to 12 percent of ruptured brain aneurysms, Evans says.
"When somebody has the worst headache of their life occurring during sexual activity, that's the first thing to rule out," he says.
But for most people, it's not an aneurysm. If headaches become the routine price of an orgasm, the condition can improve with weight loss, exercise, adopting a passive role during sex or prescription medications taken before sex.
A few people find that sex is just what the doctor ordered.
A study in the May 2001 edition of Headache found that was true for 27 of 57 women who reported having sex during a migraine. Intercourse provided complete relief for 10 of the women, and 17 said they experienced temporary or modest relief.
One of Evans' patients immediately left work at the first sign of a migraine.
"He'd run home and go find his wife," he says. "His headaches got better with sex."
Susan Brink writes for the Los Angeles Times.