Habituation: “Give me a pain that I’m used to!”

by Carolyn Thomas   ♥   @HeartSisters

When I first read about a pain study called “Give Me a Pain That I Am Used To”, it made perfect sense to me.¹  Published in the journal Nature: Science Reports, this came out about the same time I was diagnosed with osteoarthritis a couple of years ago – which I did NOT see coming.  Ironically, breathtakingly painful arthritis symptoms (starting in my left knee and right hand at that time) felt far more debilitating to me than the daily chest pain of refractory angina I’d been living with since my 2008 heart attack.

This may seem counter-intuitive. We know that chest pain can be a dangerous and even deadly symptom. Knee and wrist pain is rarely if ever fatal! It occurred to me that maybe I was feeling extremely distressed by my new arthritis symptoms because I’d simply not yet become habituated to the new pain in the way I’d already become habituated to my longstanding cardiac pain.

As Tali Sharot and Cass Sunstein explain habituation in their fascinating book Look Again:  The Power of Noticing What Was Always There:

“Habituation is the tendency of neurons to fire less and less in response to things that are constant.”

Neurons are the nerve cells in our central nervous system, which includes the brain and spinal cord. These nerve cells send and receive signals to the brain.

There are two basic steps to feeling pain:

1. The actual cause of the pain – for example, swollen arthritic joints or a heart attack. Neurons signal our brains to pay attention – especially to something different happening in our bodies.

2. The brain’s perception of the pain – do we shrug off the signals, or do we stop everything and focus on what hurts?

When an Emergency Department physician sent me home in mid-heart attack with an acid reflux misdiagnosis, I felt so embarrassed about making a fuss over nothing that I shrugged off the neurons’ alarm signals – and immediately went back to work. After that morning, I attributed all of my symptoms to indigestion – because a man with the letters M.D. after his name had confidently told me to do so. It took me two full weeks until the central chest pain, nausea, sweating and pain down my left arm became so unbearable that I forced myself back to that same Emergency Department. Different doc this time, different (and correct) diagnosis: the “widowmaker” heart attack.

Sharot and Sunstein explain the basics of habituation like this:

“You enter a room filled with fragrant roses and after a short while, you cannot notice their scent any longer.

“Or if you’re repeatedly exposed to a bad smell, you may initially find it too strong, but over time, you may become habituated – and no longer even notice it.  Your brain cares about what recently changed, not about what remained the same.”

Habituation applies to both good experiences (“Those roses smell beautiful!”) and to bad ones (“I have chest pain!”) – and even to mundane ones. Cass Sunstein suggests that right now, for example, you probably have some kind of vague noise on in the background that you’re barely even noticing anymore.  The noise is still there, but your neurons no longer feel like sending you that message. (He also cites his co-author Tali Sharot’s research on vacations. She found that that 43 hours into a new vacation seems to be the peak of holiday happiness. You may still like the hotel/the meals/the pool after the first two days, but not nearly as much as you loved them at the beginning. You’ve become habituated to what were the “firsts” of your experience (checking into your hotel, seeing your room for the first time, your first dip in the pool, your first fancy cocktail before dinner) and your neurons have simply stopped communicating to your brain what’s no longer new. (For maximum benefit, should we all be planning 2-day vacations from now on?)

In either example, roses or pain, neurons can begin to slow down their messaging to the brain once we become habituated to whatever is constant.

Consider also how our central nervous systems can be tricked.  I first learned about tricking the nervous system in the pain self-management work of Neil Pearson, founding chair of the Canadian Physiotherapy Pain Science Division. Here’s how Neil described this:

“Taking a pain pill that you believe will help you means that your sensation of pain actually begins to decrease even before the medication has had time to be absorbed into your bloodstream.

“But what if you suddenly realize that you’ve run out of those trusty pain pills? Because you now believe that you cannot get the immediate help you need, your nervous system suddenly pays more attention to the neurons’ pain signals, and you will feel more intense pain.”

Habituation is also the approach that therapists use in what’s called exposure therapy. For example, exposure therapy has been helpful to many people in helping to reduce symptoms of aerophobia, an extreme fear of flying in an airplane.

This therapy involves gradually exposing a person to something they’d normally avoid because it makes them frightened or anxious – but this time in a very controlled environment. In the case of aerophobia, this exposes the person little by little to places, thoughts or situations relating to air travel – like visiting an airport, or watching planes take off and land.

In the journal paper that I mentioned, the lead author was Austrian scientist Dr. Katharina Paul, who reports that adapting to persistent and non-avoidable pain is a very important mechanism in the body.  This kind of chronic pain can “lead to the dramatic impact of serious impairments in daily quality of life² and even increased mortality related to abnormal endocrine stress responses.” ³  She adds a major benefit to habituation:

“Habituation allows preserving our physical, emotional and cognitive resources.” 

Because I’m already habituated to frequent chest pain, I’m generally relieved of worrisome panic about every daily twinge. That’s a good thing. But habituation is present in both good and bad experiences, as the Look Again book explains:

“Even exciting relationships, stimulating jobs and breathtaking works of art can lose their sparkle after a while. Many people stop noticing what is most wonderful in their own lives.

“They also stop noticing what is terrible.They get used to dirty air. They stay in abusive relationships. People grow to accept authoritarianism and take foolish risks.”

Reduced habituation to pain in patients living with severe chronic pain (meaning that these people’s pain rarely feels reduced) has been mainly reported in diagnoses of migraine, chronic low back pain and fibromyalgia.

By the way, please note the neutral word “reduced” in that last sentence.

Unfortunately, many pain researchers, when comparing habituation between two groups of people, still use terms such as impaired habituation.  Dr. Paul herself wrote that “syndromes associated with severe chronic pain seem to be characterized by defective habituation to painful events.” 

Regular Heart Sisters readers already know my opinion on how such words matter in medicine. Researchers’ unfortunate use of words like “impaired” or “defective” is a perfect example of how hurtful this patient-blaming language can be. For more background on words that matter, see also: “Heart Failure:  It’s Finally Time to Change the F-Word” (my editorial in the BMJ Open Heart journal).

Speaking of researchers, chronic pain research here in Canada where I live is still poorly funded. The funding stats are grim (as they are in many countries). The proportion of research dollars here is approximately 41 times higher for cancer than for chronic pain.

While I seem to have habituated by now to cardiac chest pain,  I’m discovering every day some new painful function to add to the list of simple activities I can no longer take on because of arthritis pain. Tying my shoelaces with my newly gnarled fingers, for example, is not possible anymore. Because shoelace tying is a relatively short-lived pain for me, I haven’t yet habituated to my feelings of extreme frustration. Instead, I went out and bought red Ara walking boots with zippers, not shoelaces.

And yes, I’m helped by my doctors, and by physiotherapists at our local Hand Clinic, and by credible resources, classes and exercises from the Arthritis Society of Canada. I now wear a skookum wrist brace to help manage the pain in my right hand, and an even bigger orthopedic brace that stabilizes most of my left leg –  which enables me to take longer walks without suffering for hours afterwards. But I still find myself wondering some days: “Why did this happen? And how much worse is this going to get?”

As Sharot and Sunstein write in their book, habituation affects countless common situations in life.  And sometimes, it may even help us get used to living with cardiac pain.  I can hardly wait for it to kick in for my arthritis pain!

♥

1. Paul, K. et al. “Give me a pain that I am used to: distinct habituation patterns to painful and non-painful stimulation.” Sci Rep 11, 22929 (2021).

2. Breivik, H. et al.  “Survey of chronic pain in Europe: Prevalence, impact on daily life, and treatment.” European Journal of Pain 10,  287–333 (2006).

3. Torrance, N. et al.  “Severe chronic pain is associated with increased 10 year mortality: A cohort record linkage study.” Eur. J. Pain 14, 380–386 (2010).

Image: Alexas_Fotos, Pixabay

Q:   How have you become habituated to one or more of your medical symptoms?

♥

NOTE FROM CAROLYN:   I wrote much more about pain in my book, “A Woman’s Guide to Living with Heart Disease” (Johns Hopkins University Press). You can ask for it at your local library or favourite bookshop (please support your independent neighbourhood booksellers) or order it online (paperback, hardcover or e-book) at Amazon – or order it directly from my publisher, Johns Hopkins University Press (use their code HTWN to save 30% off the list price).

See also:

When Heart Disease Isn’t your Biggest Problem

You Won’t Always Feel This Way

When You Ignore Pain Because You’re Used to It

Dear Carolyn: “I Couldn’t Tell if My Pain was ‘Normal”