Are Mental Disorders Brain Disorders?

Anneli Jefferson

• Publisher: Routledge
• Year: 2022
• ISBN:
  9781000617719
• Edition: 1
• Topic: Philosophie
• Subtopic: Esprit et corps en philosophie

The question of whether mental disorders are disorders of the brain has led to a long-running and controversial dispute within psychiatry, psychology and philosophy of mind and psychology. While recent work in neuroscience frequently tries to identify underlying brain dysfunction in mental disorders, detractors argue that labelling mental disorders as brain disorders is reductive and can result in harmful social effects.

This book brings a much-needed philosophical perspective to bear on this important question. Anneli Jefferson argues that while there is widespread agreement on paradigmatic cases of brain disorder such as brain cancer, Parkinson's or Alzheimer's dementia, there is far less clarity on what the general, defining characteristics of brain disorders are. She identifies influential notions of brain disorder and shows why these are problematic. On her own, alternative, account, what counts as dysfunctional at the level of the brain frequently depends on what counts as dysfunctional at the psychological level. On this notion of brain disorder, she argues, many of the consequences people often associate with the brain disorder label do not follow. She also explores the important practical question of how to deal with the fact that many people do draw unlicensed inferences about treatment, personal responsibility or etiology from the information that a condition is a brain disorder or involves brain dysfunction.

1 Introduction

DOI: 10.4324/9780367822088-1

1 The controversy surrounding ‘brain disorder’ labels

We often hear that specific mental health conditions are brain disorders or diseases. For example, the American Psychiatric Association characterizes schizophrenia as a chronic brain disorder (APA 2020). The authors of the Research Domain Criteria (RDoC), which is a system for classifying domains of psychological and brain function proposed by the United States’ National Institute of Mental Health, also work on the assumption that mental disorders generally are brain disorders. We often hear statements like ‘depression is a chemical imbalance in the brain’. At the same time, many scientists and philosophers strongly oppose characterizing conditions like depression, schizophrenia or bipolar as brain disorders. In a recent opinion piece in Nature, neuroscientist Carl Hart argued that categorizing addiction as a brain disease is both inaccurate and harmful to people suffering from addiction (Hart 2017). Psychologist Richard Bentall argues that viewing mental disorders as brain disorders gives us a skewed view of these conditions that does not take into account people’s life history and the experiences that precipitated their mental distress.

We find ourselves in a strange stand-off: on the one hand, we have people saying that viewing mental disorders as brain disorders is the way forward in understanding and treating psychiatric conditions and applying this label will lead to more empathy towards people affected. On the other hand, many object that this view of psychiatric illness is both incorrect and harmful. According to both sides of the debate, there is a lot at stake in how we characterize these disorders, so we need to get this right.

Most people in the debate endorse a broadly materialist world-view, according to which mental processes depend on the brain, so the disagreement does not rely on fundamentally different assumptions about the mind-brain relationship such as, for example, Cartesian dualism.¹ So why do researchers, clinicians and philosophers disagree so violently as to whether conditions such as addiction, schizophrenia, bipolar disorder or depression are brain disorders? In a recent piece defending the brain disorder view, neuroscientist Camilla Nord states: “I suspect the heart of the disagreement originates from people’s vastly different ideas of what it means to say that something is a ‘brain disorder’” (Nord 2021). This is the correct diagnosis, the main source of disagreement is a conceptual one, regarding the question what a brain disorder is. But, as with many stubborn disagreements, it isn’t the case that we have clearly articulated conceptual differences – most of us aren’t even sure what we mean by ‘brain disorder’, even if we have strong views on what isn’t a brain disorder. While we agree about established cases of brain disorder such as neurosyphilis or Chorea Huntington, we lack good criteria for deciding how to categorize controversial cases such as addiction. Put differently, we may agree that a condition is a brain disorder when there is something wrong with the brain, but we don’t agree on what differences from normal functioning count as there being something wrong with the brain.

The problem with discussions about brain disorders is that there are a number of ill-articulated presuppositions at play which lead to unhelpful confusion and disagreement. The two interconnected questions that will be running through this book are ‘What is a brain disorder?’ and ‘What is the relationship between mental disorders and brain disorders?’. One important result from this book is that we have made so little progress on the second question because we don’t have a clear answer to the first. So, I will propose criteria for dysfunction in the brain. On my account, mental disorders are brain disorders if they involve brain dysfunction, but they need not be caused by a preceding defect in the brain.

2 Methodology

Which mental disorders are brain disorders is an empirical question, but it requires a theory of what makes something a brain disorder. My aim is to answer this theoretical question. My approach to these issues is not an empirical but a philosophical one, clarifying the models that are used in the debate and their implications. The primary focus will be on what theoretical presuppositions underlie disagreements about brain disorders, and how these could be resolved. To illustrate the contrast to the empirical project, one could argue about whether addiction involves dopamine disregulation; this is an empirical question, and scientists need to look at the brains of healthy and addicted individuals to resolve it.

But often, the conceptual and the empirical are intermingled in these debates. We sometimes hear that bipolar disorder must be a brain disorder, because taking lithium helps to treat the symptoms. Or some say that depression cannot be a brain disorder because there is no single biological cause. These kinds of statements are of interest because of their hidden presuppositions. Working backwards from the claims made about brain disorders, I will tease out the presuppositions behind such claims and show what theories of brain disorder they commit people to. My own positive account will be theory driven, laying out conditions on when brain difference should count as brain dysfunction. Whether these conditions are met by mental disorders such as depression, schizophrenia or anorexia is, in the end, an empirical question. However, I will explain what kind of evidence and findings would support the claim that these conditions are brain disorders. Before embarking on the book’s main argument, I will say a few words to explain what I mean by disorder and dysfunction, two key concepts in the book. I then distinguish my project from a related but slightly different discussion about the nature and benefits of the bio-psycho-social model of mental disorder versus the medical model.

3 Dysfunction and disorder

Much of this book will address the question of what a brain disorder is. But before addressing that in the main text, I want to briefly define the notions of mental disorder and of dysfunction, which are also central to these debates. People disagree about what mental disorders are and whether they exist in the first place; some feel they are better understood as problems in living. A further question is whether psychiatry even needs the concept of disorder in order to go about its business of treating people suffering from mental distress (Bortolotti 2020). I will not enter into these debates, but assume that we can make sense of the notion of mental disorder, even if there are borderline cases, where it will be hard to decide whether a condition should count as pathological. Dimensional approaches are increasingly popular in psychiatry, and if these are correct, the traits and symptoms that we have in extreme forms in conditions like schizophrenia, depression or obsessive compulsive disorder will often be present in less pronounced ways in the non-clinical population. So we should expect a certain amount of vagueness at the boundaries between health and illness.

I will be endorsing a hybrid account of mental disorder, according to which a mental disorder both requires psychological dysfunction and needs to meet a harmfulness criterion. In other words, I am not endorsing a purely naturalist account of mental disorder, which holds that mental disorders are conditions that do not require any normative judgements about desirability or rationality. (For a supposedly value-free account of mental disorder, see Christopher Boorse (1977).) Rather, I assume that in order to count as a disorder, a condition needs to be undesirable because it is harmful to the individual. While judgements of harm and desirability are frequently more controversial in the realm of mental health, we need to make these judgements even in the realm of somatic medicine. It may be more obvious that freedom from pain or a longer life expectancy are desirable, but we are still making an evaluative judgement when we say that they are.

Both dysfunction and harmfulness are necessary ingredients to an account of mental disorder: dysfunction is necessary, because not all disvalued and harmful states are considered disorders (so a harmfulness criterion cannot be sufficient). For example, Jerome Wakefield mentions the states of poverty and ignorance. Both are harmful to the individual, but they are not considered disorders (Wakefield 1992a). At the same time, not all psychological difference and not even everything described as psychological dysfunction is harmful to the individual or its environment, and harm is an essential part of our understanding of mental disorder.

3.1 Psychological difference/dysfunction

Physical or mental disorder requires dysfunction, whereby some organs or psychological processes in the agent are not operating as they are supposed to. As Wakefield has pointed out, this just raises the further question of how we decide what an organ, psychological mechanism, etc. are supposed to do (Wakefield 1992b). There are a number of options for addressing that particular gap, some of which aim to do more work than others. When is a difference in functioning a dysfunction? I take the broadest possible line here in order to avoid turf wars in the philosophy of medicine and biology. According to Robert Cummins (1975), we can define functions as contributions of a constituent part to the activity of a system it is embedded in. So, for example, the heart’s function is to pump blood and this contributes to the transport of oxygen through the body. Other accounts of function define the function of an organ, trait or mechanism as its species-typical contribution to an organism’s survival and reproduction (Boorse 1977) or as a selected effect (Wakefield 1992a, 2000, 2017b, Garson 2011, 2019).² What all these accounts have in common is that they think of function as a typical contribution of a trait/organ/mechanism to a larger scale goal or activity. Evolutionary or selected effect accounts of dysfunction think that we need to appeal to the effect a certain trait has had in the past which explains its retention in a population over generations. Many philosophers favour aetiological or evolutionary accounts of function partly because they think that this is what biologists mean by function (Garson 2019), but also because they provide a way of saying what something is good for without having to appeal to values. In this book, I will take dysfunction to be the failure of a trait or mechanism to contribute in the usual way to a system level capacity the organism has. Whether these contributions (functions) are selected for is a further question that I will remain agnostic about in this book.

3.2 Harmfulness

Both the notion of disorder and, to a lesser extent, that of dysfunction presuppose that there is something wrong with the agent. Unless one thinks that we can get the ‘something wrong’ out of evolutionary history, we will need to locate it in the fact that a condition is harmful to the person who has it. There are, of course, a bunch of thorny issues here, most prominently to what extent harm arises from the condition itself or from the way the social environment reacts and interacts with the person suffering from the condition. Famously, homosexuality is no longer considered a disorder because we came to the conclusion that in as far as homosexuality was harmful, this harm was caused by society’s reaction to it, rather than by homosexuality itself. This means that our concrete diagnostic categories may need revision. (There are then further questions to be asked – whether it is sufficient for meeting that pre-condition if a mental health condition is typically, but not invariably, harmful to the individual (APA 2013, Cooper 2020).) While there are many tricky issues lurking in the background, in what follows, I will be assuming that mental disorders involve both psychological dysfunction and some form of harm.

4 Adjacent debates – the bio-psycho-social model and the medical model

The view that mental disorders are brain disorders is often equated with the medical model of mental disorder and contrasted with the bio-psycho-social model of mental disorder. On some readings, the medical model sees mental disorders as akin to somatic disorders and focuses on explanations and treatment methods that target the body, in the case of mental disorders, the brain. By contrast, psychotherapeutic approaches, heavily influenced by psychoanalysis, focus on psychology alone, and the bio-psycho-social model takes into account biological, psychological and social factors in its approach to mental illness (Roache 2020). Many authors now endorse the bio-psycho-social model for psychiatry (Bolton and Gillett 2019) and reject the medical model (though see Huda (2019) for a defence of the medical model that nevertheless acknowledges the importance of social and psychological factors).

While there is clearly an overlap between this debate and the issues I am interested in, my question is more narrow. My question is when we should say that there is something going wrong in the brain of someone suffering from a mental disorder that would justify speaking of a brain disorder. This is a much narrower focus, which is in principle compatible with different approaches to causal explanations for how someone got the condition in the first place and with different approaches to treatment. Furthermore, Engel’s original proposal of the bio-psycho-social model stressed that we should take the psychological and social more seriously in both psychiatric and somatic conditions (Engel 1977). So it’s not well suited to distinguish between different kinds of conditions. That biological and social factors should be attended to is a fairly well accepted point at this stage, as we know that things like low socio-economic status or loneliness are risk factors for somatic conditions as well and need to be considered in prevention and treatment (Huda 2019).

With these preliminaries in place, we can start tackling the main questions: what does it take to be a brain disorder; and can mental disorders be rightly labelled as brain disorders?

5 Outline of the argument

I will proceed as follows: in Chapter 2, I present and criticize one account of brain disorders that is prominent in the literature. On this narrow view of brain disorders, modelled on paradigmatic conditions such as neurosyphilis or brain tumours, mental disorders are indeed not brain disorders. However, as I will show, this account does not provide clear criteria for what it takes to be a brain disorder and so ends up being theoretically barren. When we say that depression is in many ways different from a classic brain disorder such as brain cancer or Parkinson’s, we haven’t said anything very informative. And the general criteria proposed either don’t apply to all brain disorders or they are weak enough to be compatible with more modest accounts.

I then proceed to present my positive account in Chapter 3, which develops an account of mental disorders as brain disorders I first introduced in my paper “What does it take to be a brain disorder?” (Jefferson 2020b). On my account, a condition is a brain disorder if it is h...