The FIT Criteria – A Framework for Considering Whether Chronic Pain and Symptoms Could be Neuroplastic

As we prepare for our upcoming Masterclass in Mindbody Medicine with Dr Howard Schubiner, our team is reflecting on his groundbreaking work including the FIT criteria explored in this blog.

Understanding the origins of chronic symptoms: a common problem

A major challenge of living with chronic symptoms is that the causes are often uncertain: around 40% of primary care visits involve symptoms without a clear medical explanation.

It’s essential to work with a doctor to rule out structural issues like fractures, tumours or infections. However, identifying the true sources of chronic pain or symptoms isn’t always straightforward. Research shows that imaging findings such as MRIs or X-rays don’t always match pain, and many people have ‘abnormalities’ without symptoms.

Neuroscience evidences that many chronic, unexplained symptoms in fact stem from nervous system changes and dysregulation rather than physical damage. These are known as neuroplastic or mind-body symptoms.

This is positive news because, neuroplastic symptoms can be reduced and resolved using mind-body approaches that target the brain and nervous system.

If you’ve ruled out underlying medical conditions with your doctor, it can be helpful to use an assessment tool to consider whether your own symptoms could be neuroplastic.

The FIT criteria: a helpful framework for assessing chronic symptoms

Dr. Howard Schubiner’s FIT criteria offer a practical way to evaluate chronic symptoms. This checklist highlights key patterns—functional, inconsistent, and triggered—that are common in neuroplastic symptoms.

Dr Howard Schubiner is a leading expert in mind-body medicine with decades of experience treating unexplained chronic pain and symptoms. The FIT criteria are based on his extensive clinical experience along with his research and teaching, which has advanced our understanding of neuroplastic symptoms and how to identify them.

In essence, the FIT criteria provide a simple checklist to help identify symptoms that are caused by learnt neural pathways and nervous system dysregulation rather than structural problems or illness in the body. Using this framework can provide clarity and reassurance, helping you to better understand the origins of your symptoms.

Breaking down the FIT criteria

The FIT criteria divide symptoms into three key patterns: Functional, Inconsistent, and Triggered:

• “Functional” means the issue affects how the body works rather than its physical structure.

• “Inconsistent” refers to symptoms that vary in intensity, quality, location, or timing.

• “Triggered” describes symptoms that arise in response to harmless or non-threatening stimuli.

  
  

These patterns reflect the hallmarks of neuroplastic symptoms – and are very different to patterns of symptoms caused by injury or illness. For example, if you cut your finger, the pain clearly relates to tissue damage and tends to behave in predictable ways. For example, you would expect the pain to be localised to the injury and gradually ease with healing time. It would not be triggered by innocuous stimuli such as the time of day or weather changes.

Functional Symptoms

‘Functional’ symptoms refer to problems with how the body operates rather than damage to its physical structure. In other words, a software difficulty rather than a hardware one. For example, you might experience an overactive bladder due to anxiety before a big presentation at work (functional symptom). The symptoms experienced during a urinary tract infection might be very similar but the cause is different (structural symptom).

To consider whether your symptoms are functional, you might ask yourself:

• Did my symptoms arise without a clear injury or cause (either out of the blue or gradually over time)?

• Have my symptoms persisted beyond the expected healing time and standard medical treatment?

• Have my symptoms shifted or spread to different areas of my body over time rather than remaining localised as seen with acute injuries?

• Do I have symptoms in many different parts of my body? (The nervous system may be what connects them all.)

• Have my symptoms become symmetrical or do they occur along one whole side of the body (patterns that are much likely to be structurally caused)?

Inconsistent Symptoms

To consider whether your symptoms show inconsistency, ask yourself the following questions.

• Have my symptoms changed location over time? Pain that moves around—such as starting in the neck, then appearing in the shoulders or head, or switching sides of the body—is less likely to be caused by a single structural issue.

• Do my symptoms fluctuate in intensity or quality over time? Symptoms that vary throughout the day, sometimes severe and other times barely noticeable without a clear physical reason are less likely to be structural.

• Do I get temporary relief from physical therapies? Short-lived improvement after treatments like massage, reflexology or acupuncture can reflect shifts in the nervous system (such as relaxation or expectation), rather than resolving a physical problem.

• Do my symptoms respond to stress? Symptoms that appear or intensify during or after stressful situations highlight a mind-body component.

• Do my symptoms improve when I am distracted or enjoying myself? If symptoms fade while you’re engaged—like during a fun outing, a great conversation, or a hobby—but return when stress or routine resumes, this suggests neuroplasticity. Structural injuries don’t pause in these situations.

Triggered Symptoms

A further hallmark of neuroplasticity is when symptoms are set off by harmless or unrelated triggers. This reflects a learnt, conditioned response—where the brain begins to associate certain cues with symptoms, even though they aren’t physically causing harm.

Ask yourself:

• Do my symptoms respond to neutral stimuli? This might include weather changes, specific foods, the time of day, etc.  

• Do I experience symptoms in response to light touch or benign stimuli such as wind or cold?

• Are my symptoms triggered by my thoughts? In some cases, simply thinking about a stressful event, person, or situation can bring on symptoms. This would not occur with structural symptoms.

  
  

Together, these patterns show how the nervous system can “learn” symptoms —an encouraging sign, because learned patterns can also be reversed.

Embracing FIT criteria to support neuroplastic healing

Answering ‘yes’ to any of the questions above indicates that your symptoms might be neuroplastic. But remember, you don’t need to tick all the boxes to ‘rule in’ neuroplasticity.

Over the coming days and weeks, revisit this checklist and build your own evidence list, noting down any times you notice your symptoms behaving in a functional, inconsistent or triggered way. These are clues of neuroplasticity.

Growing your evidence list over time can help to build confidence in the neuroplastic explanation for your symptoms. The more confident and reassured you feel that your body is not physically harmed, the more you will be able to interrupt the symptoms-fear cycle that fuels neuroplastic symptoms. Breaking this cycle is at the heart of mind-body healing.