The Inflamed Mind Read online

  It’s depressing being ill

  Do you remember Mrs P? The woman with arthritis who was depressed, as you would be, wouldn’t you? When I look back on that moment of ordinary medical practice in an NHS outpatient clinic, I am struck by the complexity of the ideas buried deep beneath the assumption: you would be depressed, wouldn’t you? (If you were in her shoes.) The words imply, to put it less succinctly, that Mrs P had consciously reflected on her situation. She knew she had rheumatoid arthritis, she knew that it was inexorably getting worse, her body was becoming ever more disabled, it wouldn’t be long before she couldn’t leave her wheelchair. She could certainly foresee her progressive decline to a dismal end. And knowing this had made her depressed. As anyone would be depressed who knew that they shared her fate.

  When I consulted a senior physician about her combination of depression and inflammatory disease, that was his theoretical analysis. And there is some truth in it. He was right that it is depressing to know that you are ill, or that your illness is likely to get worse. But he was not so right in his unspoken assumption that “thinking about it” was the only possible way in which a physical illness could cause depression. What it meant in practice was that Mrs P’s depression was not his problem. He was a consultant physician, concerned with the physical aspects of her health. Her depression was a normal psychological reaction to her physical disease, it was not rooted in her body and unrelated to the pathological cause of her swollen joints. It lay beyond his domain of expertise - in the realm of the shrink or the priest. There was nothing he could do.

  It’s an anecdote, admittedly, but not an exceptional case. Two aspects of Mrs P’s experience are shared by many other people with rheumatoid arthritis. First, her mental symptoms are not unusual. About 90% of arthritis patients say that fatigue is their principal problem and about 40% are depressed. A sense of “brain fog”, or difficulty in thinking and planning clearly, is also common. Psychological symptoms dominate the lists of “unmet clinical needs” compiled by the big arthritis charities and patient advocacy groups. The combination of depression and rheumatoid arthritis, which I thought was so remarkable about Mrs P, turns out to be commonplace, even if still largely invisible.17

  The second aspect of her experience that many other arthritis patients might recognise is the apparent indifference of her physician. The specialist doctors, called rheumatologists, who attend to most cases of rheumatoid arthritis, pay most attention to evidence of physical disease - fMRI scans of eroded joints and blood tests. That is what they are trained to do and very good at doing. They are much less attentive to psychological or behavioural symptoms. Rheumatologists often don’t ask their patients about their energy levels, feelings or thoughts at all. If patients volunteer information about their lethargic, pleasureless states of mind, their physicians may not know what to do, or even what to say. Because they certainly can’t say to the patient what they, like Mrs P’s consultant, might be automatically thinking: “Yes, I’d be depressed too, if I was you.”

  What is going on here? Why is something so common, and so important to patients, so reflexively neglected by doctors? Why is the close link between depression and arthritis hiding in plain sight? I blame Descartes.

  The cogito, God, and the machine

  René Descartes was a 17th-century mathematician and philosopher, not a rheumatologist or an immunologist. Yet his ideas continue to exercise a remarkable degree of influence on modern medicine. Cartesian dualism, his most medically important philosophy, is the idea that there are two kinds of thing in the world; there are two domains of experience. There is an outer, physical world, where objects interact with each other mechanistically, by experimentally verifiable rules. And there is an inner, spiritual world, where subjective ideas and emotions form the content of consciousness or one’s sense of one’s self. Each one of us is divided in two by dualism. Our bodies belong to the physical, objective, unconscious domain and our minds to the spiritual, subjective, conscious domain.

  Descartes reached this conclusion in a curious and original way. He started from radical doubt. He sceptically challenged himself to verify everything he thought he knew about the world. He was deeply mistrustful of sensory information as a reliable source of knowledge because in his dreams his senses were actively misleading. He could see and hear and feel things in his dreams that weren’t really there, he realised when he woke up. So he asked himself how he could be sure that the apparently real things that he could see when he thought he was awake, and walking around with his eyes open, were any more real than the things he saw when he was dreaming with his eyes closed. How could he be sure that the world around him wasn’t a dream from which he had not yet woken?

  Ultimately, Descartes decided, the only certainty that survived such extreme doubt was doubt itself. While he was restlessly, rigorously, sceptically cogitating on what he knew, what he didn’t know, what he knew he knew, what he didn’t know he didn’t know, etc, etc, the one thing that Descartes knew beyond doubt was that he was cogitating. I doubt everything, I don’t think anything is real, I think it’s all a dream. I can think whatever I like. But however sceptical or dismissive of the world I feel inclined to be, I cannot doubt my doubting self. “I think I am not real” is a contradiction in terms. If I can say that to myself then I know without doubt it cannot be true. Or to put it the other way round, cogito ergo sum, I think, therefore I am, must be true.

  Those are the most famous words he wrote but Descartes is also often remembered as one of the principal architects of the scientific revolution, one of the founding fathers of modern science, his name uttered in the same breath as those of his close contemporaries Galileo and Newton. Yet it is not immediately obvious how these two aspects of his reputation can be reconciled. How could a man who has reached the solipsistic conclusion that he knows nothing with certainty, except his own thoughts, be the same man who is credited with setting the world on the path to a more certain scientific knowledge of almost everything? The answer, perhaps surprisingly, was God.

  Descartes was a devout Catholic writing at a time, just after the Reformation, when religious belief was more culturally mainstream and more intensely debated than it is now. Descartes believed that he was an immortal and materially insubstantial soul and this soul was what animated his thoughts, his doubts and every other species of his consciousness, including his moments of communion with God. Following a medieval line of reasoning, Descartes argued that his cosmic vision of a perfect and infinite God could not have been falsely invented or misinterpreted by him, because God transcended his human, mortal and finite capacities for imagination. A man couldn’t simply imagine God if God didn’t exist. The fact that men of advanced reason, like Descartes, commonly could conceive of God was proof positive that God existed. His belief in a benevolent God was axiomatic: not only was God real but God had to be real.

  And Descartes believed that God would benevolently protect him, and others like him, from error if they used their mental faculties as diligently and critically as possible to make sense of things. It was God that made the rest of the world potentially knowable to Descartes, rescued him from the certain isolation of knowing only cogito ergo sum and opened his mind to experimental science.

  As Descartes used mathematics to define the abstract physical mechanisms that controlled the appearance of things, he began to think of the world as a machine. He saw the human body as a machine, built up of many component parts - like nerves, blood vessels and muscles - which interacted with each other according to the same physical laws that governed the mechanisms of animals and inanimate machines. Physics was the trunk of the tree of scientific knowledge, said Descartes, meta-physics (aka God) was the root, and all other sciences were branches off the trunk. This vision of the body as a physical machine, which Descartes was arguably the first person to see and to articulate compellingly, was the prospectus on which the whole extraordinary success of biology and scientific medicine has since been built.

  Of cou
rse, at the time, Descartes didn’t have a clue what was really going on in the human body. Understanding how the body machine was built was the business of anatomy, which in practice meant dissecting human corpses. This had been widely forbidden for religious reasons for at least the previous 2,000 years. The first anatomical drawings of the heart and the brain that look reasonably accurate to a modern eye did not begin to appear until about 100 years before Descartes. Understanding how the body machine actually worked was the business of physiology and this was in an even more primitive state. The 17th-century physician, William Harvey, had just published the first correct theory on the circulation of the blood at about the same time as Descartes was incorrectly assuming that the blood was expelled from the heart by being heated and expanded in some way.

  If the first drafts of the Cartesian body machines now seem to be full of errors and absurdities in detail, they still seem remarkably ambitious in scope. Descartes may have known almost nothing about the body machine compared to what we know now, but he was convinced that all would be knowable, and that ultimately all of animal life would be explicable by the physical mechanisms of the body. For animals, it was simple. They did not have a soul, just the machine. For humans, it was not so straightforward. The mechanistic physics of the body could not be allowed to explain everything about a human as this would exclude the meta-physics of the soul. And the soul was a given, for Descartes; it was real and it had to be. So he was forced to the compromise that there must be a body machine, and there must also be a soul, and both must be combined to make a human. But what then did the soul do, that the body couldn’t do? Where was the soul located in the body? And how did the soul and the body interact?

  His own efforts to answer these questions never satisfied Descartes.18 High intellectual prowess and divine communion were surely spiritual; but what about emotions and memories - could they be entirely animal, ultimately explicable by the laws of physics? The bodily location of the soul was also difficult to pinpoint anatomically. Descartes considered a number of possible candidates before settling on the pineal gland, a small and otherwise obscure structure that had recently been dissected in the human brain. Descartes liked the look of the pineal gland because it was singular and central, whereas most of the brain is symmetrically organised. There is a pair of cerebral hemispheres, right and left, and most of the component parts of the brain machine are duplicated in both hemispheres. This would not do for the location of the soul because of its unique and indivisible nature. There were a few other singular structures in the brain, like the pituitary gland, which might conceivably provide suitable accommodation for the soul; but Descartes preferred the pineal gland because he thought it was more mobile.

  These anatomical factoids shakily supported his mechanistic theory for how the body and the soul could interact (Fig. 4). He imagined that “animal spirits” could percolate from the blood into the pineal gland and that the visual scene detected by the eyes was also projected onto the inner walls of the gland, where it was consciously perceived. So the pineal was a place where the body machine could speak to the soul. Descartes also imagined the movements of the pineal gland could provide a mechanism for the soul to command the body. He thought the pineal gland worked as a kind of valve or tap, ceaselessly active as it controlled behaviour by directing the flow of spirit through the nerves to the muscles of the body.

  That position roughly marks the end of his extraordinary 20-year intellectual journey: from doubt, to the cogito, through God back to the machinery of the world, and ultimately to the conceptual and anatomical awkwardness of deus ex machina, the God in the machine that is supposedly a human being. Descartes was nothing if not sceptical about his own ideas. He knew that dualism raised as many questions as it settled, and he was still working on it, when suddenly he died.

  Descartes was a man of independent means, having inherited property and therefore not financially driven to do work he didn’t want to do. He preferred to live alone, often changing his address to protect his privacy, until, inadvertently, he found himself obliged to deliver philosophy tutorials to the Queen of Sweden three mornings a week from 5 to 10am, a time of day when he naturally preferred to lie in bed, cogitating. One cold and dark February in Stockholm, he developed a chest infection and was dead within 10 days, aged 54. Several years later, his final but inconclusive work was published on the mind/body problem, a problem that didn’t so clearly exist before him, a problem that he invented but didn’t resolve.

  Figure 4: A lady trying to explain the pineal theory of the human mind and body. This is one of the engravings in Descartes’ final work, “Treatise of Man”19 showing how light from an arrow is refracted through the lenses of the eyes to send a visual signal down the optic nerves (coming out of the back of each eyeball), to the pineal gland, drawn as a large droplet or pine seed-shaped thing, marked H, and positioned roughly where you’d expect her right ear to be. The optics and geometry are tip-top. The idea of linking a visual stimulus to a motor response by a physiological circuit is very advanced for the time and remarkably close to the 19th-century concept of a nervous reflex. But the brain anatomy is terrible, even by 17th-century standards. The pineal is drawn in the wrong place and about 10 times bigger than it really is, completely unconnected to the rest of the brain, and connected to the eyes and muscles only by lines of ink on the page. The soul’s location has been named but not nailed.

  A long shadow

  We now know that the details of Cartesian dualism, in its original form, are all wrong. The pineal gland plays a much humbler part in the human body machine than its pivotal, dynamic role in Descartes’ scheme. It is a biological clock, sensitive to the daily and seasonal cycles of daylight, and part of the physiological system that maintains a regular, circadian rhythm of alertness and activity every 24 hours. The pineal is important but not of cosmic significance. It doesn’t move much, it doesn’t control the flow of fluid through the ventricles, it isn’t connected to every nerve fibre in the body, it isn’t spiritually attuned. If the pineal gland is damaged or lesioned by disease, the patient may complain of a disrupted sleep/wake cycle, but she will not experience disembodied consciousness, a pure state of mind, uninformed or uncontaminated by anything in the physical world.

  If Cartesian dualism was an ordinary scientific theory, it would have been decisively refuted long ago by the mismatch between what Descartes proposed the pineal gland was doing and what it actually does. However, dualism has powerfully endured not so much as a scientific theory but as an idea - one might even say an ideology - about what aspects of human experience are scientifically tractable, and therefore medically respectable.

  The Cartesian vision of a human body machine reigns triumphant in medicine. There is universal consensus that the body is made up of atoms and molecules, cells and organs. We can measure it in units like millimetres and seconds. We can expect it to obey universal laws of physics and to be comparable to the biological structures and functions of other animals. All of this makes it scientifically tractable. It may not yet be scientifically understood in every detail but there is no reason to think that it won’t become ever more understood in future. And as we have achieved greater scientific understanding of the body, historically, so we have won some therapeutic battles in the fight against disease. We can feel medically in control and progressive about the bodily side of the dualist divide.

  But the other side of the human condition - by dualist definition - is something else, embarrassingly different to modern scientific and medical minds. Descartes talked about it unashamedly in spiritual terms; but that was then, 400 years ago, a time when religious idealism still permeated European culture. Descartes also thought he needed God to protect him from experimental error; but the intervening centuries of splendid scientific achievement have made us cockier. We are now confident (with good reason) that we have the logic and the technology safely to do science unchaperoned by God. We have generally reached the view that God has nothing to do with scien
ce and science has nothing to tell us about God. So what on earth are we supposed to do about the God in the Cartesian machine?

  We can call it the mind or the psyche or consciousness or unconsciousness, instead of the spirit or the soul. We can call it whatever we like. But still it doesn’t exist in physical space. It is not clear how it should be measured, if it can be measured at all. We have no reason to expect that it will obey laws of physics, or that other animals have spiritual or mental experiences that are comparable to those of a human mind. And, following the ignominious collapse of the pineal theory, it remains unclear how this mind thing should be related to the body or the brain. All of which makes the mental domain seem scientifically intractable, now and in the future. We do not have the mind under the microscope, we can’t see the component parts of its mechanism and therefore we can’t expect to be as therapeutically effective in treating diseases of the mind - if it even makes sense to use that expression - as we have become in treating diseases of the body.

  However much we admire his scepticism, and celebrate his revolutionary vision of the human body as a machine, Descartes also bequeathed us a conundrum that scientific medicine hasn’t yet cracked. In Cartesian medicine the mind and the body aren’t the same, they’re different kinds of thing, and we still don’t know how they are connected to each other. The body is the domain of the physician and knowable by physics and other sciences. The mind is the domain of the psychiatrist or psychologist and knowable only by introspective guesswork, or by inference from behaviour. In Britain in 2018, the NHS is still planned on Cartesian lines. Patients literally go through different doors, attend different hospitals, to consult differently trained doctors, about their dualistically divided bodies and minds.