Sunday, October 30, 2011

Meditation and pain

'You're going to be in pain' is the general idea of the first noble truth, usually translated grimly as 'Life is suffering'.  The other noble truths conspire to tell you what's causing the pain (being thirsty) and that there's a way out of it.  I suppose that the orthodox prescription is to adopt the ethical practices of the eightfold path, thus reducing your thirst for things and so your annoyance when you don't get them (or your disappointment when you do).  But is there any evidence that meditation itself can reduce pain?  Isn't the idea that the mind can influence the body a load of hippy shit?  And even if I think that meditation is helping my headaches, couldn't I just be wrong?

In the early days of my headaches, I tried a number of different therapies, some conventional and some less so.  I tried to get an idea through the popular press about what therapies had scientific support and what did not.  I went to various chiropractors, who would give my neck sharp twists, as if they were trying to finish me off around the wrong corner of a Steven Seagal film.  I found out that though there's a cultural bias in the research, there's a relatively good amount of evidence suggesting that acupuncture can help with one or two conditions (mainly idiopathic headaches and nausea), but it didn't work for me.  I went to an osteopath who - I could swear - could make my right arm weaker or stronger by adjusting my neck (and no, I've never been able to figure out how that worked). 

Compared to the uncertain evidence supporting many alternative therapies, studies suggesting that meditation helps reduce pain are rather numerous (though some are vitiated by a lack of proper controls).  In the 1980s Jon Kabat-Zinn conducted a series of experiments at the University of Massachusetts Medical School involving subjects in chronic pain who were invited to take part in a ten-week course in mindfulness meditation.  There was a statistically significant decrease in reported lower levels of present pain, negative body image, and pain-related depression among the patients who completed the course, and no significant improvement on any of these dimensions by members of a control group, who were given more conventional treatments such as nerve blocks, physical therapy, and antidepressants. 

More recently, a research group at the Université de Montréal compared pain tolerance in 13 Zen practitioners (with over one thousand hours of meditation each) to that of 13 non-meditators (with no or little experience of meditation).  The researchers placed heating plates on the subjects' calves, and warmed them up to between 43 and 53 degrees Celsius.  The meditators tolerated greater levels of pain in both meditative and on-meditative states.  More recently still, scientists at Wake Forest University subjected 15 people to the same level of heat before and after a course consisting of only 80 minutes of meditation, and found that the individuals reported significantly less discomfort after the training (and that the reported reduction in sensation was accompanied by differences in brain activity).

But meditation happens in the mind, while pain affects the body, so how does that work?  There are two common misconceptions here: one is about how pain works and one is about the relationship betweend mind and body.  As its happens, both misconceptions could be attributed to Descartes, although both ideas have an insidious plausibility that makes it likely that people have often come to them independently.

The first unhelpful notion is that pain is a signal that travels along a nerve from a stimulus (the tack you stepped on) to the brain (which registers the sensation); pain represents an accurate signal of damage to tissues.  Fortunately and unfortunately, things are actually more complicated than that.  In fact, there's no reliable link between how much you're hurt and how much pain you're in, as suggested on the one hand by soldiers who get their arms blown off and don't feel any pain until they're out of the combat area (lots of damage, no pain), and on the other hand by sufferers of chronic pain (lots of pain, not always much continuing damage).  The neurologists Ronald Melzack and Patrick Wall drew attention to cases like these and explained them with their gate-control theory of pain, in which downward inhibitory signals from the brain (saying 'I can't take in that pain signal now because I have to protect my comrades in battle') and constantly-reinforced signals (saying 'your head must still hurt because the experience of that car-accident was so traumatic') have as much to do with what you feel as what is happening to your body.

The second unhelpful Cartesian idea is dualism, that mind and body are two separate substances.  The theory has of course been extensively debunked over the last four hundred years for a number of reasons, chief among them the philosopher's inability to give any satisfactory account of how the two separate stuffs could possibly interact with one another.  And yet the assumption that the mind can be conceived of as existing separately from its physical substrate underlies many of the thought-experiments that seem still to be in vogue (as in Hofstadter and Dennett's collection, The Mind's I).  Against this backdrop, the more of an uncompromising monist you are (believing either that everything is completely mental, like Berkeley, or that everything is entirely physical, like Hobbes), the more likely you are to comprehend how meditation has an effect on physical pain.  Meditation can reduce pain because it impacts the brain, and the idea that the neurological control-centre might have an effect on the peripheral nervous system should not be considered an outrageous one.

Sometimes I wonder whether the benefits I'm deriving from meditation are just all in my mind.  That is partly why I like to look up scientific studies, to reassure myself that all the time I'm investing in meditation isn't being wasted.  But in my better moments I realize that this is a peculiarly ridiculous kind of doubt.  The benefits of meditation are, of course, all in my mind - it's just that my mind includes my body (or, if you want, they're all in my body, which is also where the mind is).  And in any case, can I really be wrong about my own state of pain?  Pain is a subjective state, and if the relief I'm perceiving is merely subjective, that's fine with me.  In the end, whatever regions of my brain are lighting up when I meditate, and whatever neurons are firing or being generated, all that really matters for me is that sitting down on my own, without any desire to get well or change things, makes being or not being in pain not really matter so much at all.

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