What is central sensitization?

Central sensitization: the back story to just about every story I tell on this blog. I’ve written the phrase a million times, but always in passing, always with a link to an article somewhere else. I think it’s high time the topic gets its own post.

Practice Makes Perfect

We’ve all heard the phrase “practice makes perfect,” right? When you want to get better at something, you practice. Want to learn how to play the piano? Practice. Want to learn how to ride a bike? Practice.

Photo: t.spang

Our nervous systems are always changing and growing, in response to the things we do. Our brains form new connections all the time.

This is how we learn how to control our fingers, and move them more quickly and in more complicated patterns, when we practice the piano. It’s how we learn to balance when riding a bike. It becomes second nature.

Photo: Alan Levine

Unfortunately, the same thing can happen when you give your nervous system enough changes to “practice” sending pain signals.

It sounds crazy, but basically, our nervous systems get better at sending these signals. It doesn’t happen automatically– you won’t develop central sensitization if you stub your toe, or get stung by a bee.

But it can happen if the pain goes on for long enough. For example, central sensitization can happen to someone who’s hurt their back, and has been in pain for a few months. The nervous system has been sending these pain signals over and over again, and now– just as if the person had been practicing the piano for a few months– the task has gotten easier.

Central sensitization can also occur in someone who has suffered a larger degree of physical trauma in a shorter time period. For example, it can happen to someone who’s had surgery– even if they were under anesthesia at the time.  Consciousness isn’t required for central senstization to occur.

This is because central sensitization involves nerves, your spinal cord, and the parts of your brain that process pain without conscious thought. They are still learning how to process all those pain signals, even if you are under anesthesia. (Of course, I’m not saying this will happen to everyone who has surgery. It is, however, a possibility).

In a nutshell, central sensitization means the central nervous system becomes more sensitive.

Photo: Maryl Gonzalez

There are many different ways in which central sensitization can manifest itself– the symptoms are not always the same from person to person.

The differences have to do with the person’s individual genetic makeup, what the original illness or injury was, and other health issues the person may have. (And yes– the person’s beliefs and perspective on pain can have an impact on how they respond to central sensitization, but they do not cause it. More on this later– I have very strong feelings on the subject!).

Invisible Illness

Scientific research has shown that central sensitization tends to be present in patients suffering from many of the conditions people generally refer to when they talk about “invisible illness.” These conditions include fibromyalgia, chronic regional pain syndrome, migraine, temporal-mandibular joint disorder, chronic pelvic pain, and irritable bowel syndrome.

Sometimes central sensitization is the root of the problem: for example, researchers now generally believe it to be the cause of fibromyalgia (please, please don’t believe the other things you read!).

In other cases, central sensitization is one of several contributing factors (still playing an important role, however). This is more likely to be the case in conditions such as irritable bowel syndrome, which can also be influenced by food intolerances/imbalances in gut bacteria, and temporal-mandibular joint disorder, which involves the physical pathology of the joint. In these cases, central sensitization perpetuates the problem and causes additional pain and discomfort, but is not necessarily the primary cause.

The Common Link

Because central sensitization is the common cause, it makes sense that so many patients with fibromyalgia also suffer from other “invisible illnesses.” For example, studies have shown that significant numbers of fibromyalgia sufferers also have irritable bowel syndrome.

I have so much more to say on this topic– more research to tell you about, the history of how it was discovered, as well as my own personal stories.

But…. as I have to keep reminding myself, I’m writing a blog, not a textbook… so all of that will have to come in future posts!


I think it’s important to always post links to scientifically-valid articles when I talk about scientific/medical concepts.

Here is a great plain-English overview on central sensitization, written by Christina Lasich, M.D., for HealthCentral.net.

Next, an incredible overview of the science on central sensitization from Paul Ingraham of PainScience.com, which is an amazing website.

Ingraham’s article is actually a “jargon-to-English” summary of this important review of the scientific literature on central sensitization written by Clifford Woolf, the researcher who first discovered central sensitization back in 1983.

Finally, check out this equally important article from Muhammad Yunus, who has done vital work exploring the common links between central sensitization and the invisible illnesses (he calls them central sensitivity syndromes in this article).

I realize that the average reader might not be able to understand all of the scientific terms in these articles (I know I struggle), but I want you to know that legitimate and credible information is out there, and this is what it looks like.

A Note to My Readers:

I am always happy to answer any questions that you might have.  I think that all of this information is so important for us to be aware of as chronic pain sufferers!  It can really be life-changing, once you start to truly understand the roots of your condition.

I am always so curious to know what you think! Did you already know that central sensitization is believed to be the cause of fibromyalgia?  Does the common link between fibro and other invisible illnesses make sense to you? Let me know!

Why do some hospitals get away with charging such exorbitant prices?


The Center for Medicare and Medicaid Services published a ground-breaking report yesterday looking at the average prices charged by 3,000 U.S. hospitals for the “top 100 most frequently billed charges.”

The report shows that different hospitals appear to charge wildly different prices for the same procedures, seemingly without any rhyme or reason.  While one hospital might charge $5,304 for a hip replacement, another might charge $223,373.

While it’s true that the same types of procedures can be more or less intensive depending on whether or not the patient experiences complications, this study was based on an averaging of costs.  This means that the data is unlikely to be skewed by patients with complications.

Here are a few more choice pieces of data, as summarized by the Washington Post:

  • For heart failure with major complications, the average price ranged from $13,960 at one hospital to $75,197 at another.
  • For kidney failure with major complications, the average price ranged from $16,366 at one hospital to $80,919 at another.
  • To treat esophagitis and digestive disorders, the average price ranged from $7,107 at one hospital to $37,750 at another.
  • The prices charged by for-profit hospitals to Medicare were, on average, 29% greater than the prices charged by nonprofit or government hospitals.

Unfortunately, I wasn’t too surprised by some of these findings.  I think that, at this point, pretty much everyone knows someone who’s been screwed over by a crazy hospital bill.

One example is this story about Robert Reed, a patient who was charged $1,525 by a hospital he had not even been to.  Reed had had a procedure performed by a dermatologist who was affiliated with the hospital, but whose physical office was 1.5 miles away.  The doctor only charged $354 for her services, but the hospital charged $1,525 in fees for an “operating room” and “facility” Reed had not even been to.  This kind of price inflation is legal, and it happens all the time.

If you ask me, this is the problem with the American healthcare system.  Until now, medical institutions have been able to keep their prices a secret.

I can’t think of any other industry where it’s legal to keep the price a secret from the consumer until after he or she is legally obligated to pay it.  Buying clothes at a store?  There’s a price tag on them.  Getting your hair cut at a salon?  There’s a sign on the wall with prices on it.  Buying a car?  There’s paperwork to fill out once you and the salesperson have come to an agreement.

Now, to be fair, the prices hospitals list for various procedures are often much higher than the prices individual patients are asked to pay.  For one thing, many insurance companies have their own special “agreements” with hospital networks.  I see this on my own medical bills all the time: the first few lines represent the “actual” price which the hospital would like to charge, and the next few lines show what is called the “allowed” charge—in other words, the special deal my insurance company worked out as part of its contract with the hospital.  As the subscriber, the price I pay is based off of the “allowed” charge, not the much-higher “actual” charge.

But as you can see from the Center for Medicare and Medicaid services report, these “special agreements” don’t do much to level the playing field in the long run.  When hospitals are able to inflate their charges to Medicaid and health insurance companies by tens of thousands of dollars, we all pay in one way or another.

Regardless of where you stand on the political spectrum, it should bother you that up until now, hospitals and other medical institutions have been able to ride roughshod over the consumer.  If you’re inclined to defend these hospitals out of a belief in the “free market,” I’d like to point out to you that it’s not a free market when consumers are unable to make informed decisions.  If we are going to rely on competition to reign in cost, consumers need to be able to know the estimated cost before they undergo a medical procedure.

This report was step in the right direction, and I am cautiously optimistic about the future.  The Center for Medicare and Medicaid Services says that the report is part of an increased push for transparency in the healthcare industry on the part of the Obama administration.  I think we can all agree that the price discrepancies shown this report are totally ridiculous.  Private hospitals may have the legal right to set their own prices, but we as consumers ought to be able to know what those prices are, just as we would for any other purchase.

**Money picture published by 401 K (2013) under a Creative Commons license.

Someday there could be a test for fibromyalgia


One of the reasons I am so optimistic about the future is that someday I believe we will have a way for doctors to see just how much pain a person is in.  It won’t be a matter of taking the patient’s word for it (though that should be enough) or wondering whether or not a patient is faking it.  Instead, there will objective results right on the screen.

What I am talking about is functional magnetic resonance imaging, or fMRI.  An fMRI is slightly different from what most people think of as an MRI.

A regular MRI takes “snapshots” of what is going on in the body.  Your doctor might send you for an MRI of your spine if you are suffering from back pain.  Sometimes women have breast MRI’s if something odd shows up on a mammogram.  An MRI shows you what is happening in the body at a particular moment in time.

An fMRI, on the other hand, is a way of looking at blood flow in the brain.  It shows which parts of the brain are more active than others.  Because the more active parts of the brain require more oxygen, an fMRI will show increased blood flow to those areas.

Researchers working with fMRI have been able to identify distinct patterns of brain activity in the brains of chronic pain sufferers.  These patterns of activity set chronic pain sufferers apart from normal, healthy individuals.  These distinct patterns are unique to people with chronic pain and are sometimes referred to as a “pain phenotype.”

I have heard of several research groups in the US who are investigating whether or not pain sufferers can learn to “rewire” their brains using the information given in an fMRI.  This is done by using a form of biofeedback.   There is evidence to suggest this can be done.   (If you would like to know more about biofeedback, check out these great explanations by Christopher DeCharms and Dr. Sean Mackey).

I’ll be writing more on the idea of biofeedback in a later post.  For now, the fact that an fMRI can even show pain activity is exciting to me.  In a world where chronic pain/fibromyalgia patients are routinely pushed aside, dismissed, and belittled, fMRI offers us all hope.

People who really understand pain know that it can be a disease in its own right.   Once a person’s nervous system gets wound-up enough (yes, “wind-up” is actually one of the scientific terms that refers to this process), the pain can be out of control, and no longer in proportion to whatever physical injury might have originated it.

With brain imaging, this phenomenon will become more clear.  Perhaps someday, pictures of the “pain phenotype” will  appear in everyone’s medical school textbooks.  A sympathetic doctor won’t be something we have to travel far and wide for, like the pot of gold at the end of the rainbow.  Pain will be understood as a disease in its own right, and perhaps then adequate pain medication can actually be given.

Or… who knows.  Maybe pain patients won’t need as much medication because instead, we will be able to learn to control the pain-processing parts of our brains using biofeedback.

Either way, I am optimistic!

For more information, you can check out a new page in my Resources section called “Brain Imaging for Chronic Pain.”


**Ok, so this photo is actually a picture of someone’s heart, but it looks a lot like the fMRI’s I’ve seen in documentaries.  I know there are better pictures out there, but I get nervous about that whole copyright infringement thing, so for now I’m sticking to what I can find in Creative Commons.  Thank you to Glyn Nelson.**

Above rainbow picture courtesy of SugarBear1956 on Flickr

Do you believe in qi?

Do you believe in qi? “When I practice qi gong or t’ai qi, I do not trouble myself with whether or not the qi is “real.” Qi gong is an art. I practice it in a beautiful way. Like Japanese cuisine, it works best when it looks good. To do a thing in a beautiful […]

“Science-based” vs. “evidenced-based” medicine

Over the years, I’ve seen the words “evidence-based” used to justify a lot of concepts I find dubious.  (Trust me– I saw some pretty ridiculous things during the time I worked in a mental health group home).

This article from Paul Ingraham at PainScience.com in favor of moving from evidence-based to science-based medicine was music to my ears.  I realized that, although I hadn’t consciously thought of it in those terms, advocating for that shift has been one of my motivations for working on this blog.

A lot of the treatments for fibromyalgia sufferers might be “evidenced-based,” but that doesn’t mean they shed any real light onto its causes.  For example, an “evidenced-based” course of treatment for someone with chronic pain or fibromyalgia might be cognitive-behavioral therapy.  It’s true that multiple studies have shown CBT to be helpful for patients with these conditions.

However, I don’t believe it’s reasonable to infer that because CBT has been shown to benefit fibromyalgia patients, those patients must have had an underlying psychological problem in the first place which contributed to their fibromyalgia.

To me, that’s confounding variables.

It makes perfect sense that someone with chronic health problems is going to appreciate having a sympathetic person sit with them, listen to them, and teach them new coping strategies.  However, this does not mean that fibromyalgia or related conditions are caused by depression or anxiety.  It simply means that therapy helps patients feel better.


What I try to do on this blog is to present the scientific evidence in favor of what I’m arguing.  That’s why I am always linking to academic articles.  Even though I know people don’t always have time to read them, it’s important to me that the citation is there.

It blows my mind that there are still practicing medical professionals out there who are unaware of all the research that has been done on the complexities of the nervous system, and how people experience pain.  In my opinion, the research that has been done on the process of central sensitization is a lot more convincing than the research that has been done on the overlap between mental health conditions such as depression and anxiety and fibromyalgia.

For one thing, it makes sense that you’re going to find a higher rate of depression and anxiety among the chronically ill.  I don’t know why anyone is surprised by this. To me, it makes perfect sense that those suffering in chronic pain and discomfort would experience an impact on their mental health.  It’s a chicken and the egg problem, and I find those studies relatively meaningless.

For another, the people who write these studies apparently don’t know anything about the process of central sensitization.  They appear to be completely unaware of the ways our nervous systems can physically change in response to chronic pain, in a way that is beyond our control.  Physical abnormalities have been found not only within the brain but within the spinal cord of chronic pain sufferers.

To say that depression and anxiety are responsible for chronic pain is to focus on only the tip of the iceberg.  If the people who published these studies would at least acknowledge the rest of the iceberg, I would be able to take them more seriously.

But it seems that academic knowledge is too compartmentalized.  Some people go into psychology and study people’s moods and thoughts.  Some people go into neurology and study the nervous system.  Even the people within neurology end up specializing.

This is why I am inspired to see people beginning to criticize the concept of “evidenced-based.”  I’m tired of people throwing those words around as though it means what they are doing is automatically great.  There is a difference between evidenced-based and science-based.   When you can see physical abnormalities in the brain of a chronic pain sufferer under a fMRI, that is science.   Assuming that people with fibromyalgia must have a problem with depression because psychotherapy makes them feel temporarily better is not. 

Anyway, that was a bit of a rant (but I’ve been told my rant-y posts are some of my best!).

Do you agree with me? Disagree? Let me know your thoughts!