There are many labels used to describe chronic pain that doesn’t have a clear medical explanation—terms like central sensitization, psychogenic pain, nociplastic pain, and pain system hypersensitivity, just to name a few.
But according to a paper published in the journal PAIN, the International Association for the Study of Pain (IASP) recommends a simpler and more unified term: Primary Chronic Pain.
Here’s how I usually explain it to my patients:
“There are two basic types of pain: primary and secondary.”
Let’s start with secondary pain—because it’s the easier one to understand.
If someone hits their thumb with a hammer and it hurts—what kind of pain is that?
Secondary pain. It’s secondary to a clear physical injury.
If someone sprains their ankle or breaks a hip? Still secondary pain—because there’s a structural explanation.
What if the pain comes from kidney stones, an infection, or rheumatoid arthritis?
Again, that’s secondary pain. There’s a known medical cause behind it.
Now, let’s talk about primary pain.
This is the kind of pain that can’t be explained by another diagnosis. It’s often accompanied by emotional distress—things like anxiety, frustration, grief, or anger. The pain might show up in one area, or it might be widespread. But no scan or blood test can fully explain it.
The key difference?
Secondary pain usually heals with time, or can be treated with medications, therapies, or even surgery. But with primary pain—though it’s very real and felt in the body—the solution doesn’t come from the body.
And that last part is important. With primary pain, the healing often begins not by fixing the body—but by understanding the nervous system, calming the mind, and shifting the relationship with pain itself.