Philosophy Part 6: Are mental disorders brain diseases ‘in waiting’?


In the last blog 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.

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 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 (1;2). 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 ‘biopsychosoicial 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 aging (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 towards a brain-based origin.

Again Wittgenstein’s insights are useful here (see Blog 2 of this series). 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’ (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 those biological psychiatrists and others who argue that some mental disorders are brain diseases and Szasz, 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 the last two blogs, 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.


Next: So what are ‘mental disorders’?








(1)    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.

(2)    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.

(3)    Jaspers K. General Psychopathology (trans. J.Hoenig & M.W. Hamilton). Manchester: Manchester University Press; 1968.




7 thoughts on “Philosophy Part 6: Are mental disorders brain diseases ‘in waiting’?

  1. Thank you for yet another, very interesting blog. If I may add a personal note, it would bother me if someone were to tell me that my depression is a disease ‘just like diabetes’ because to me, what I think and feel has to do with past experiences, with who I am and how I interact with my surroundings. The disease-model seems to rob my experience of its meaning. I don’t expect someone with diabetes to feel quite the same way about it.

  2. You write the following: “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.”
    Surely a “neurological condition” is absolutely always potentially detectable in the brain (or nervous system) – by virtue of its being a physical neurological condition. What “is and is not a brain disease” is not really a question of judgement, but of science. Until a disease is categorically scientifically identified, how can it be said to exist at all?

    • Also – how can a “neurological condition” be completely “identified” by its manifestation in behaviour? Surely this is a category error. Surely a “neurological condition” can only be fully and unequivocally identified by a physical examination of the B.C.N. – brain and central nervous system – of some kind.

      • Hi citizen sofa,
        this is not the case. Dementia, including Alzheimer’s disease, is not diagnosed by brain imaging or any other physical tests. As a group, people with a diagnosis of dementia have more of the brain pathology associated with aging than those who do not (plaques and tangles and infarcts identified in brain scans), but most people at a certain age have some of this pathology and there is overlap (ie. a person without dementia may have more pathology than an individual with it). Brain imaging cannot therefore be used to make a diagnosis, and no other physical tests specifically identify dementia either. Dementia is diagnosed by someone’s behaviour and performance on tests of cognitive function.

        I think people do not realise this because if you look at information on diagnosing dementia it is very vague and does not make this clear. When someone is being investigated for possible dementia, they will have various blood tests and other examinations, but these are for the purpose of excluding other diagnoses (like hypothyroidism) that may be producing the symptoms. Dementia is diagnosed when no other physical explanation of the symptoms (behaviour and cognitive deficits identified on testing) is found.

  3. Pingback: Philosophy Blog 7: So what is mental disorder? Part 1 Reasoning and meaning | Joanna Moncrieff

  4. Pingback: Philosophy Part 8: So what is ‘mental disorder’? Part 2 The social problem | Joanna Moncrieff

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