If you are a red-headed women with fair skin you may be less sensitive to pain than other women — and men for that matter. And more responsive to a particular painkiller.

Then again, maybe not. Jeffrey Mogil, one of Canada's leading pain researchers, turned the scientific world on its ear three years ago when he discovered that red-headed women with a particular genetic makeup have a distinctive response to pain and its treatment.

Since then, however, a team of American researchers have found almost exactly the opposite, though still distinctive, reactions when it comes to pale-skinned red heads with the so-called Viking gene (Mc1r, as its known in the lab).

But Mogil, a psychology professor at McGill University in Montreal, is not in the least perturbed. "The truly weird and exciting thing," he points out, "is that any such gene would have an impact on pain in the first place."

Indeed, it does seem kind of weird that genetics or gender could play a role in anything as elemental as being hurt.

But in the last decade or so, psychologists and other pain researchers are coming around to a new definition of just what is pain — and how the experience looks to be different in men and women.

Gone is the old telegraph model that served medical science for thousands of years: You put your hand in a hot fire you felt the pain of the burn until the tissue eventually healed.

In its place, some scientists are putting forward the notion that pain ricochets through the body more like the way the internet works: The initial experience sets off a complex chain of reactions involving one's general health, genetic makeup, brain chemistry and perhaps even how one has come to think about pain in the first place.

This more complex understanding has led to psychologists categorizing pain in two broad categories, Mogil observes. One of these is Good Pain, the kind that teaches you to keep your hands out of fire. The other is Bad Pain — the chronic pain that afflicts so many and seems to have more to do with how the brain itself transforms the initial stimuli and fails to shut itself off.

Men and women

One of the more intriguing directions pain research has been is to delve into the differences between men and women, both as they experience pain and as they respond to different drugs.

Some of these differences are no doubt cultural. Little boys are often taught to be stoic about their "ow-ies" from a very young age, whereas girls are often allowed to be more expressive.

But upbringing alone doesn't seem enough to account for the fact that women suffer from migraines, arthritis and debilitating conditions such as fibromyalgia anywhere from three to nine times more than men do.

What's more, in routine pain experiments on mice, as well as on college students (asking them to stick their arms in buckets of freezing water for as long as they can), scientists have clearly demonstrated that the males and females of the species have noticeably different thresholds for when they first notice pain, and different tolerances of how much they can withstand.

More importantly, perhaps, researchers have also discovered that the brains of men and women process pain differently. A different set of genes, neural circuitry and chemicals are involved for each sex.

For men (and the same is true for male mice), a particular chemical receptor is engaged whenever the body experiences good pain. It's a different one for women and lady mice.

One result of these studies is that men appear to respond better to a certain class of drugs (NSAIDS or non-steroidal anti-inflammatory analgesics) whereas women get stronger pain relief from narcotics.

One University of California study even found that a certain type of analgesic used in dentist offices works fine on women but actually enhances the pain in men.

Blue pill, pink pills

All this research, particular that with a genetic component, is likely leading to better gender-specific doses, Mogil says. But he is also one of those who believe that in the not-too-distant future, drug companies will be making entirely different gender-specific drugs — like, say, blue pills for boys, pink for girls.

This is a subject not without controversy. So far, there has only been one study that claims to have found a painkiller that works only on women and not on men. (Mogil's red-headed experiment found that the analgesic pentazocine worked for all men and women; it just worked noticeably better in those with the Viking gene.)

But clearly there are gender preferences when it comes to analgesics, and doctors in the ER and obstetrical wards are constantly adjusting their doses to accord with the latest research.

What science hasn't been able to come up with, though, is a balm for chronic pain. Nothing seems to work for that, not even the strongest opiates.

The bad or chronic pain that doctors seem to be seeing much more of, where even the slightest touch can send some patients into fits of agony, appears to be a function of the brain being unable to turn off its own alarm circuit. The pain signal just seems to go around and around in a high intensity loop and neither narcotics nor anti-depressive drugs appear able to shut it off.

Many people develop chronic pain from major surgeries, including up to 80 per cent of amputees. To try to stem this, York University psychologist Joel Katz has been encouraging certain Toronto hospitals to use pre-emptive analgesia, beginning before the actual operation, to try to stage manage the body's response to pain all the way through the procedure.

Much, though, is clearly in the deep recesses of the mind. Two years ago, for example, researchers in London and Pittsburgh hypnotized otherwise healthy people and told them they were in acute pain. Brain scans then showed these subjects had virtually the same electro-chemical activity as patients with actual ailments — another indicator pain can actually originate in the mind.

Then there was the famous fake-knee operation that researchers at Baylor College of Medicine in Houston carried out in 2000 on those seeking common arthroscopic surgery for arthritis. Some had the actual surgery, some had a dummy operation in which small incisions were made but nothing else was done.

Neither group knew for at least two years what treatment they had undergone but the results showed that those who had the placebo surgery were just as likely to feel pain relief as those who'd had the real thing.

Just another example of the fact that when it comes to pain, the brain seems to have a mind of its own.