How Clifford Woolf discovered central sensitization (and why you shouldn’t blame yourself for chronic pain)

You’ve probably noticed that my blog is all about central sensitization— the process through which the central nervous system can change over time and become more sensitive to pain.

Personally, I find learning about central sensitization to be empowering.  I spent years trying to find an answer for the pain and other symptoms I felt, only to be told by various medical professionals that my problems were in my head, the possible result of depression or anxiety.

I knew, deep down, that this just wasn’t true.  It’s not that I was unwilling to believe that mental health factors could play a role.  But it just didn’t resonate. I didn’t feel anxious or depressed.  I felt like I was in pain, and wanted it to stop.

That’s why, when I first heard the phrase central sensitization and looked up what it meant, I was so struck.  Because there was a way to explain why my nervous system was acting funny, and causing me to feel things other people didn’t feel, that wasn’t based on my mental health.

So.  How do we know about central sensitization?

A neuroscientist named Clifford Woolf discovered the process of central sensitization back in the early 1980’s.  In 1983, he published a well-known and often-cited letter to the respected scientific journal Nature outlining his theory, entitled “Evidence for a central component of post-injury pain hypersensitivity.”

Although the scientific community didn’t quite accept Woolf’s ideas right away, ultimately he ended up sparking a new wave of research, and his theory of central sensitization is generally accepted today (although much more work still needs to be done).

Basically Woolf ended up discovering central sensitization more or less by accident, in the process of researching something else.

(Now, I’m not a huge fan of animal research, so I don’t love what I’m about to describe to you.  But I am grateful for the results, so for the sake of understanding, here we go).

Woolf was studying the “withdrawal reflex” that caused the rats to jerk their paws away from a painful stimulus.  He tested them over and over again, over the course of a day, and he noticed that he started to get different results at the end of the day.

After a long day of testing, the same rats were much jumpier.  It became much easier to trigger their withdrawal reflex.  They would jerk their paws away even at things that shouldn’t have been painful, or wouldn’t have caused them to react that way at the start of the day.

Woolf realized he was seeing completely different behavior in the same rats, and under the exact same conditions.  Only one thing had changed: their nervous systems had been “practicing” the withdrawal reflex all day long, and were now responding to stimuli differently.  He hypothesized that somehow, the central nervous system had changed to become more responsive to pain, after exposure to repeated stress.

Woolf’s theory was pretty revolutionary at the time. Generally speaking, the scientific community believed the central nervous system always processed pain the exact same way, like a simple machine performing the same task over and over.  Woolf’s discovery turned all of that on its head, by suggesting that actually, the central nervous system can be changed and shaped by its experiences.

His ideas were not widely accepted right away, but his work, along with that of others such as Muhammad Yunus, has now formed the basis for a wide body of research on central sensitization and chronic pain that’s going on today.

***

We do still have a long way to go.  Much more research is needed, not to mention new treatments to be based on that research.

However, the reason I wanted to go into detail and describe the rat experiment for you guys is this:

If you have chronic pain/fibromyalgia, people are going to tell you it’s in your head.  Unfortunately, even sometimes people who have a passing understanding of central sensitization will imply tell you it’s in your head.  In my experience, people can understand the concept of the nervous system working differently in principle, yet still think it must somehow be related to mental health.

So this is what I want you to know: central sensitization happens in rats.

Your thoughts, beliefs, and fears about pain, and your mood– those can all play a role in your experience of central sensitization/chronic pain.

But those things don’t cause central sensitization, any more than they did in the rats in Clifford Woolf’s lab.

Remember that the next time you feel someone isn’t taking you seriously.  You can’t create your whole experience of pain by “overthinking” any more than a rat can overthink something.

In some ways, your nervous system is its own being.  There are aspects of your nervous system which have way more in common with a rat nervous system than with your conscious, human mind.  (I know, think about that!  That’s evolution for ya).

So if you have chronic pain, don’t blame yourself.  Don’t scold yourself for overthinking; don’t wonder if you’re crazy.  Your body is just doing what it was always going to do, in response to whatever stress/pain/injury you experienced.

There are ways to move forward– promising ways, which I talk about on this blog.

But to me, the first step is to stop blaming yourself.   You are okay.  You didn’t cause your own central sensitization, any more than the rats caused what Clifford Woolf observed in the lab.