In her book Beyond Pain — Making the Mind Body Connection, Mailis-Gagnon says there is growing agreement chronic pain is multidimensional. To understand it, those treating it must account for its psychological, social and biological dimensions.

“On average almost 50% of the variability between people is due to genes,” says Jeff Mogil, a neuroscientist and professor of pain studies at McGill University.

“Similarly there are any number of infections or injuries that can lead to chronic neuropathic pain. Some people that get in car accidents develop causalgia,” he says.

“A lot of people are starting to think that people who are developing chronic pain is because they have some genetic susceptibility,” Mogil says.

“Who's going to get in a car accident and who isn't? And in it, are you going to injure your nerve or not? It's a lottery and the genetics are a lottery too,” says Mogil, a Canadian Research Chair in the genetics of pain.

Mailis-Gagnon believes just 40% of the variability in pain tolerance, threshold and reactions comes from genes, while a person's environment accounts for 60%.

Dr. Karen J. Berkley, a professor of neuroscience at Florida State University who's studied chronic pain for 35 years, says from the day a person is born their nervous system is being trained to decide what's painful and what's not, all to protect them and spur them to take action when needed.

“Between 45%-50% did not hurt,” Berkley says. “They started to hurt 2-3 hours later.” Everyone immediately thinks shock suppressed the pain, that it was more important after a crash to get the hell out of there.

Research indicates the same seems to hold true for little boys who are circumcised. They had far stronger negative reactions to their immunizations.

It was long thought that newborns didn't feel pain and there was a time when surgeries would be performed on them without any anesthetic. Studies have since shown that even the common practice of pricking the heels of new babies leads to increased sensitivity to pain because they were exposed to it early on.

There's no doubt sex hormones play a role and act on the nervous system, but Berkley says the field is just beginning to acknowledge and trying to understand that.

During pregnancy, a woman's pain threshold also rises. Mailis-Gagnon says sex hormones play an active role in modulating the balance of neurotransmitters, which is significant because neurotransmitter abnormalities are found in some chronic pain conditions.

Women also report more depression and psychological distress, each of which are known to enhance pain, which may also explain some of the sex differences.

There is evidence that pain can also be learned, as is the case among children who grow up around parents or close family members who experience pain.

Dr. David Corey, president of the Health Recovery Clinic, an interdisciplinary pain program in Toronto, says he always asks patients with chronic pain if they had a family member go through a similar type of problem.

Dr. Patrick McGrath, a psychologist at IWK Health Centre in Halifax and the Canada Research Chair in pediatric pain based at Dalhousie University, says it's true that modeling and reinforcement play an important role. There's no doubt if dad has a bad back and uses it to avoid work, the child is going to learn something very different than if dad does all he can to manage his pain and doesn't complain. But McGrath says physiology and psychology can't be separated.

“Family factors are important, but it's really too easy to blame the family. Psychologists are often too ready to blame mothers for anything,” he says.

Once a person has pain, it's widely accepted that focusing on it does them no favours. That's the case whether they dwell on it themselves or have others around who draw attention to it by trying to help or ease the pain.

Research in Germany looking at the brain activity of patients with back pain found that when an attentive, doting spouse was in the room, the patient felt much more pain. This was measured by functional (MRI) imaging, which saw the pain lessen when the spouse left the room.

Some people say there is always a physical injury at the root of chronic pain. But Mailis-Gagnon says there are multiple interpretations, given that in most patients, the initial physical stimuli is not that big.

Most people assume because they have pain, something is wrong with their body. But Corey says many types of pain, including headaches and charley horses, do no harm.

What isn't, however, is which comes first. That's because depression is more prevalent in people with chronic pain, but those with depression also have more pain.

There, the filter that's been at work since the day we were born, deciding what's important to pay attention to and what can be ignored, seems to be affected in chronic pain patients.

In most people, the brain is exposed to a barrage of stimuli — light, sound, smells, and internal stimuli — but it only pays attention to those that matter. That's what allows us to go through life.

Reducing that hyperactivity involves untraining the nervous system and can involve learning relaxation techniques, behavioural changes and guided imagery.

The bottom line: When pain becomes longstanding and interferes with quality of life, there's always more than just a simple injury or disease to a body part.

“More than anything else, mind and body are interconnected. If you don't put them together, you don't see pain as a whole,” says Mailis-Gagnon.

In East Africa, a surgical procedure called trepanation is done without anesthetic or painkillers, and sees the patients' head muscles cut to uncover the skull. While the doctor works, the patient is awake and holding the pan to catch dripping blood.

This is cache, read story here