Why Disease and Illness Are Concepts of the Body & Are Mental Disorders Brain Diseases ‘In Waiting’?


Editors note: this blog is a combination of two blogs originally published on Mad in America 10/11/2017, 26/11/2017

I want to come back to the work of Thomas Szasz. The last two blogs (here and here) argue that bodily states and processes need to be understood in a different way from the way we understand what human beings think and do. Mental ‘illness’ consists of things that people say and do. For Szasz, an ‘illness’ means a condition of the body, and hence mental illness is not an illness.

According to Szasz, the term ‘disease’ (in its proper and coherent use) refers to changes in bodily structures or mechanisms that produce unwanted physical sensations and experiences, otherwise known as ‘symptoms.’ ‘Illness,’ on this account, is the subjective experience that arises as a consequence of the presence of disease in the body.

On this view, a disease, in its core sense, is a property of the biological system known as the body. Hence, diseases can be described in material terms, and can be understood according to general biological principles that are independent of the individuals they affect. Diseases unfold in more or less predictable ways according to their biological nature. Cancer cells multiple and disseminate, eventually impinging on other cells to such an extent that the organs cease to function. Narrowing of the arteries supplying the heart leads to angina and heart attacks, known as coronary heart disease. It may be possible to influence the course of a disease by modifying one’s body and its environment, such as stopping smoking or getting treatment, but you cannot simply wish a disease away (or so it is generally believed). Biological systems, like chemical and subatomic reactions, are governed by predictable regularities that have nothing to do with the desires and purposes of human beings.

Little attention has been paid to the question of whether or not a disease is necessarily a bodily condition. This seems to be because philosophers of biology or disease who are not principally concerned with mental disorder just assume it to be the case, whereas those that focus on mental disorder usually ignore the issue. The French philosopher of biology, Georges Canguilhem, for example, states that “one can speak with reason of ‘Greek Medicine’ only from the Hippocratic period onward—that is to say from the moment when diseases came to be treated as bodily disorders.”1

Many thinkers who are concerned to encompass the realm of mental disorders within medicine implicitly suggest that the terms ‘illness’ and ‘disease’ do not need to refer to the body. They argue that what is essential to these concepts is the fact that they represent disvalued or unwanted states. Peter Sedgewick, for example, points out that there are no diseases in nature.2 Beyond their ability to cause pain and death, the consequences of physical conditions depend on social expectations and demands. Mild arthritis in the hands may be highly problematic to a violinist, but irrelevant to most of the rest of us. Industrialised societies organised around the productivity of wage labour heighten the impact of chronic conditions that reduce performance, which may be better tolerated in rural societies with more communal traditions.

Sedgewick is right to point out that whether the body functions adequately depends on its environment and the demands it has to meet, and these demands in turn depend on the conventions and expectations of a given society. Simply being a feature of the body is not enough to qualify something as a disease. There is also a value judgement involved about the consequences of that condition and the benefits of treating it, which will differ from one context to another.

But Sedgewick and others take the argument a step further and suggest that it is the disvalued nature of disease that is central to the concept, and therefore that other situations involving a negative value judgement can also be called a disease or illness. This is tantamount to saying that any unwanted situation can be considered to be a disease.

In response to this value-based definition of disease and illness, some thinkers have tried to reinstate objective criteria that can encompass mental disorders alongside bodily conditions. Arguing that physical or biological mechanisms and ‘psychological mechanisms’ can be thought of as equivalent, they extend the concept of illness to include situations, such as those we refer to as ‘mental disorders,’ that are defined by the presence of unwanted behaviours. Hence psychiatrist Robert Kendell argues that “the differences between mental and physical illnesses, striking though some of them are, are quantitative rather than qualitative, differences of emphasis rather than fundamental differences.”3

Jerome Wakefield’s much-discussed concept of ‘harmful dysfunction’ is an example of this thinking.4 Wakefield elides bodily dysfunction and psychological dysfunction by claiming that both are objective situations that can be defined by a failure to fulfill evolutionary purposes. However, just as the fact that cancer and crime are both negatively valued situations does not render them the same kind of thing, the idea that mental and physical mechanisms might both be evolved also does not confirm their equivalence. Our ability to be flexible and adaptable, in other words our free will, can be seen as an evolved phenomenon, but this doesn’t make human behaviour the same sort of thing as the structure of the eye or the dexterity of our hands.

Moreover, Wakefield’s reliance on evolutionary theory adds no value to the understanding of physical diseases, let alone the definition of mental disorder. Medicine uses mechanistic not adaptive explanations of function. We define the normal function of the heart, for example, as the level of functioning required to keep the rest of the body alive and well. There is no need to postulate natural selection or an evolutionary teleology.5 Indeed, evolutionary psychology has been the subject of extensive criticism, and its claims to objectivity have long been recognised as spurious. It is shot through with evaluative judgments about what ‘normal,’ ‘natural’ or ‘proper’ mental functions and behaviour consist of.6

By equating psychological and biological dysfunction Wakefield is ultimately suggesting, like Sedgewick, that there is no value in the distinction between an unwanted condition of the body and other problematic situations. Yet this is surely not true. It is evident that in real life we find it important to distinguish situations that arise as a consequence of a bodily state or event, and those that are manifestations of what we recognise as human behaviour; that is, activity initiated by an autonomous, self-directing individual. Consider the importance of distinguishing ‘real’ epileptic fits from ‘pseudo-seizures’, for example! We treat people who ‘fake’ fits, consciously or unconsciously, differently from people whose fits originate from abnormal electrical impulses in the brain.

Working in a drug detoxification unit this is a real, everyday problem. People who have been using large amounts of alcohol or benzodiazepines are liable to have epileptic fits during detoxification, which can be dangerous and life-threatening and need immediate treatment with benzodiazepines or other anti-epileptic agents. People with a history of addiction may also fake fits in order to obtain these substances, however. If you give people who fake fits anti-epileptic drugs, you not only expose them to unnecessary harm, you also undermine the ethos of the recovery programme for everyone in the unit.

We make an effort to distinguish these different situations because they call for a completely different understanding and response. Making the distinction matters.

Szasz did not deny, as is sometimes implied, that the concepts of disease and illness are what is referred to as normative — that is, they incorporate value judgements about what is ‘normal’. He merely observed that wanted or unwanted, bodily conditions can be described in material, biological terms: “although the desirability of physical health, as such, is an ethical norm, what health is can be stated in anatomical and physiological terms.”7 If you loosen the association between the concepts of illness and disease and the body, you empty them of their distinctive meaning. They are no longer able to pick out a particular category of unwanted situations and become synonymous with generic terms like ‘problem’ or ‘difficulty’. Divorced from the body, the words cease to have any discriminative power. They become meaningless.

Above, I referred to how Szasz argued that mental disorders are not rightly thought of as illnesses or diseases because these terms refer to conditions of the human body, and mental disorders consist of patterns of human behaviour. Below, I shall address the idea that mental disorders are, in fact, diseases of the body — in particular that they are brain diseases.

Some people have tried to maintain the idea that mental disorders can be thought of as illnesses or diseases by detaching these terms from their link to the body. However, we saw how this approach just empties the terms of any distinctive meaning, and leaves us unable to differentiate between situations that have distinctive implications and call for radically different reactions. In fact, because we have muddied the concept of illness so much, we have had to invent new concepts to refer to a bodily disorder — we talk of organic illness or physical illness or medical illness, for example, and the concept of ‘disease’ also sometimes works to indicate a specifically bodily condition, as opposed to ‘illness’ which is used more widely.

The other way in which people have tried to enfold mental disorders within the category of disease is by claiming that they are diseases of the body, particularly of the brain. We are all familiar with this rhetoric, which often presents the idea as if it has been conclusively demonstrated.

The website MentalHelp.net tells us, for example, that “Data from modern scientific research proves that schizophrenia is unequivocally a biological disease of the brain, just like Alzheimer’s Disease and Bipolar Disorder.”

Similarly, “ADHD is a neurological disorder that develops during childhood and can persist into adulthood.”

On another website, psychiatrist E. Fuller Torrey claims that “Since the early 1980s, with the availability of brain imaging techniques and other developments in neuroscience, the evidence has become overwhelming that schizophrenia and manic-depressive disorder are disorders of the brain.”

Despite such statements, we are a long way from finding a specific pathology that aligns with what we call schizophrenia, psychosis, depression, anxiety, ADHD, OCD or any other mental disorder you care to name. The fact that there are some subtle group differences between people with some diagnoses and ‘normal controls’ in aspects of brain structure or function does not demonstrate the presence of a neurological disease. None of the findings are specific or capable of differentiating between a person who is thought to have a particular mental disorder and one who is not. Diagnosis is still made on the basis of behaviour, thoughts and feelings that are reported by the individual or those around them, and which depend, of course, on judgements about what is ‘normal’ and what is not.

Moreover, the variations detected are most likely attributable to other differences between people who get labelled with psychiatric disorders and those who end up in the control group for studies like this, which include differences in life experiences, social class, IQ and of course the use of psychiatric medication. The most consistently demonstrated differences between people diagnosed with schizophrenia and a control group, for example, are the smaller brain volumes and larger brain cavities that show up with brain imaging technology. This research was cited for decades as demonstrating the biological nature of schizophrenia. Recent studies involving the administration of antipsychotics to animals, however, show conclusively that these differences are caused in large part, at least, by antipsychotic medication.9 No research has shown that the subtle reduction in brain size observed in people diagnosed with schizophrenia on MRI scans has anything to do with the so-called schizophrenia.

Arguing that mental disorders are not brain diseases is not to deny that biology is involved at some level, as it is in all behaviour. Many people suggest that mental disorders are a ‘bit’ biological, as well as being a bit psychological and a bit social — sometimes referred to as the ‘biopsychosocial model’. But if we think of situations that are unequivocally brain diseases, we see that where a specific abnormality of brain structure or function is causally associated with psychological or behavioural symptoms, it trumps other possibilities. If someone has multiple sclerosis (MS), their erratic behaviour is caused by the pathology of MS. If someone has hypothyroidism, their sluggishness, apathy and low mood are caused by the depletion of thyroid hormone. No other explanation is needed, although there will be social and psychological consequences, of course.

Proponents of the idea that mental disorders are brain diseases are right to point out, however, that brain diseases like multiple sclerosis, Parkinson’s disease and neurological syphilis can, and do, affect behaviour. So, it is argued, even though we may not have discovered the underlying pathology of mental disorders like schizophrenia or depression yet, surely we eventually will? Mental disorders, on this view, can be thought of as brain diseases ‘in waiting’.

For Szasz, the only criteria capable of defining a condition as a disease or illness are detectable physical signs — that is objective, material evidence of specific bodily changes. Unless these are present, a situation cannot be considered to be a disease.

However, there are some situations that we universally think of as brain diseases that do not have characteristic and distinguishing bodily features. Dementia or Alzheimer’s disease is one of these. In the early stages, there are rarely any physical symptoms, and even by the later stages there are no specific characteristics that mark out the brain of a person who is suffering from dementia from anyone else. As a group, people who have dementia show more of the pathology that naturally develops with ageing (plaques, tangles and vascular changes) than your average person of the same age, but you cannot distinguish the brain of a single individual with dementia from one without.

So does this not confirm that the situations we refer to as mental disorders can be thought of as brain diseases, even if they are not linked with any particular, observable brain pathology, as yet? I do not think this is the case, because there is something special about the ‘symptom’ of cognitive deterioration or deficiency, which is a hallmark of brain disease, that points toward a brain-based origin.

Again Wittgenstein’s insights are useful here (see Blog). Like pain, we identify dementia first and foremost as a characteristic pattern of behaviour that demonstrates the deterioration of mental abilities. Something about this situation strongly suggests to us that it originates with changes in the brain. No one argues that dementia is really a meaningful response to environmental trauma or alienation — a sane response to an insane world — as R.D. Laing is purported to have said of schizophrenia.

Back in 1913, the German psychiatrist and philosopher Karl Jaspers observed the difference between an organic condition like neurosyphilis (also known as General Paralysis of the Insane), which involves dementia, and what was already denoted as schizophrenia. He writes: “in the one case it is as if an axe had destroyed a piece of clockwork, and crude destructions are of little interest. In the other it is as if the clockwork keeps going wrong, stops and then runs again.” This appears to suggest simply that schizophrenia involves a more superficial and temporary brain dysfunction, but he went on to say: “but there is more than that. The schizophrenic life is peculiarly productive. In certain cases, the very manner of it, its contents and all that it represents can in itself create another kind of interest. We find ourselves astounded and shaken in the presence of alien secrets, which in this sense cannot possibly happen when we are faced with the crude destructions, irritations and excitements of General Paralysis.”10 (3) (P 576).

Jaspers is pointing to the different quality of behavioural disturbance that occurs in brain disease compared with the condition we call schizophrenia.

This discussion suggests that there is a line to be drawn between states where ‘behaviour’ is driven by brain processes that occur independent of the individual’s agency (rightly referred to as a disease), and other situations. In fact, there is some common ground between Szasz and those biological psychiatrists and others who argue that some mental disorders are brain diseases, in that both recognise that a disease is a bodily state with particular implications.

The difference lies in where to draw the line. Like Szasz, I think that brain disease demarcates the territory of neurology, not of psychiatry, bearing in mind that some ‘neurological conditions’ like dementia and intellectual disability have ended up within psychiatry for historical reasons. We should acknowledge, however, that neurological conditions cannot always be detected in the brain, and may only be identified through the characteristic way in which they are manifested in publicly observable behaviour. This does make judging what is and is not a brain disease a complex and imprecise matter in some cases.

Taking a cue from Jaspers, the behaviour we associate with brain disease is characterised by depletion and narrowing of our intellectual capacities and especially by a loss of the productivity and inventiveness of normal human behaviour. In contrast, the individual in the grip of a paranoid psychosis demonstrates a level of originality in constructing a delusional system or interpreting their own thoughts as alien occurrences. Depression too can involve a productive state of self-blaming, catastrophizing and pessimistic interpretations of the world. However unhelpful these forms of thinking may be, they demonstrate a level of mental sophistication and creativity that, by contrast, is destroyed by brain disease.

There are situations, however, such as very severe depression or what is sometimes referred to as ‘negative-state’ schizophrenia, where there appears to be a loss of intellectual and creative capacity. It is possible that some of these situations are associated with underlying brain dysfunction or damage. In some cases depression in the elderly appears to be the herald of dementia, for example, although in most it is not. In people diagnosed with schizophrenia with severe negative symptoms, often there are some inklings of creative thought that provide evidence that mental abilities remain intact. I recall a young man who barely spoke, and spent almost all of his time slumped in a chair with his hood drawn down, apparently doing nothing. Yet, he could rouse himself to levels of considerable ingenuity from time to time in order to obtain a supply of cannabis!

To summarise this blog, the terms illness and disease only make sense if they refer to the body. Outward behaviour can sometimes be disturbed by a bodily process, such as a brain disease, but when it is, there is a loss or depletion of mental capacities which is not characteristic of mental disorders. In the latter, creative mental abilities remain intact, even if their products are self-defeating or socially problematic.

In the next blog: So what are mental disorders?


  1.  Canguilhem G. Writings on Medicine (Forms of Living). New York: Fordham University Press; 2012, p. 35. 
  2.  Sedgwick P. Psychopolitics. London: Harper & Row; 1982
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  4.  Wakefield JC. Disorder as harmful dysfunction: a conceptual critique of DSM-III-R’s definition of mental disorder. Psychol Rev 1992 Apr;99(2):232-47
  5.  Schaffner KF. Discovery and Explanation in Biology and Medicine. Chicago: University of Chicago Press; 1993
  6.  Houts AC. Harmful dysfunction and the search for value neutrality in the definition of mental disorder: response to Wakefield, part 2. Behav Res Ther 2001 Sep;39(9):1099-132
  7.  Szasz T. Law, Liberty and Psychiatry: an inquiry into the social uses of mental health. Syracuse, New York: Syracuse University Press; 1989, p 14. 
  8. Dorph-Petersen KA, Pierri JN, Perel JM, Sun Z, Sampson AR, Lewis DA. The influence of chronic exposure to antipsychotic medications on brain size before and after tissue fixation: a comparison of haloperidol and olanzapine in macaque monkeys. Neuropsychopharmacology 2005 Sep;30(9):1649-61. 
  9.  Vernon AC, Natesan S, Modo M, Kapur S. Effect of chronic antipsychotic treatment on brain structure: a serial magnetic resonance imaging study with ex vivo and postmortem confirmation. Biol Psychiatry 2011 May 15;69(10):936-44. 
  10.  Jaspers K. General Psychopathology (trans. J.Hoenig & M.W. Hamilton). Manchester: Manchester University Press; 1968, p. 576.