What is a disease?

Imagine this, you go to the doctor for a check up. They ask you to go for a fasting blood glucose test to check you don’t have diabetes. You do the test and a week or so later you get a call asking you to come in for the results. “Your fasting blood glucose test indicates you have pre-diabetes. In other words, your blood tests show your body isn’t processing sugar as well as it should be. Don’t worry, says your doctor, your blood sugar levels are higher than they should be, but they are not yet deemed high enough for diagnosis with Type 2 Diabetes. With some lifestyle changes, you should be able to reverse the situation, says the Doctor. 

Interestingly, pre-1997 there was no such thing as pre-diabetes — at least not as a diagnosis. The standard diagnosis arose from a recommendation by the American Diabetes Association in that year intending to pick out those at higher risk of developing type ii diabetes but who do not yet have any symptoms and do not satisfy the criteria for the disease itself. 

The diagnosis itself is controversial. Indeed, a 2014 paper in the prestigious British Medical Journal argued that a prediabetes diagnosis offered little benefit to individuals and carried huge individual and societal level medical and social costs. This is because, say the scientists, the category is so broadly defined that many of those satisfying the criteria for pre-diabetes are not destined to end up with full blown type ii diabetes even without intervention. Yet, the diagnosis carries with it lots of anxiety, costs and harms to the individual, potentially without benefit (if they were not going to go on to develop diabetes at all). What is really needed, such skeptics argue, is a public health strategy to tackle obesity and inactivity at a population level as these are driving the increasing number of cases. 

This debate about whether pre-diabetes should not be a real diagnosis or not might surprise you. It is tempting to think questions of health and disease are answerable by relatively mind-independent facts. In short, there is just some fact of the matter whether you are unwell or diseased, or not. Things are not so straightforward, however. To return to diabetes. The diagnostic criteria for pre-diabetes, gestational diabetes and type II diabetes itself have varied over time and there is considerable disagreement within the medical fraternity about exactly where the blood sugar level cut-offs for these different diagnoses should lie. Too liberal, and you impose costs on people that are unwarranted. Too strict, and you risk under diagnosis and harm by failing to adequately provide care when it is needed. Ultimately, what is needed is a clear account of what it is to be healthy and unhealthy or diseased but such an account is less easy to come by than you might think. That, is the topic of todays’ episode of the p-Value

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Welcome. Today in the P-Value I’ll be talking about disease. What makes something a disease? Is it a matter of biology? Or a matter of social context? Or both? 

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When we go to the doctor and are diagnosed with a disease, what exactly are we being told? 

It is tempting to think it is just a matter of suffering. Disease is just an instance of human suffering. Alas, this is too permissive however as there are many instances of human suffering—even those that might require treatment by a doctor—that don’t seem appropriately defined as diseases. Childbirth, for example, involves significant suffering in the birthing parent but it would be very counterintuitive to say it was an instance of disease. Similarly, surgical incisions, vaccinations and even ear-piercing are all involve instances of human suffering, but none look appropriate for being categorised as disease states. Suffering also seems to context dependent. A same-sex attracted person living in a systematically homophobic state could be very reasonably said to be suffering, and severely so, but it would clearly be a mistake to therefore infer that their sexual attraction was a disease. I point to this case, because, the history of same sex attraction as being seen as a mental disease or case of mental defectiveness, is significant in this debate and something that those seeking to define disease want to ensure can’t be perpetuated.

For these reasons, theorists have looked to further criteria beyond mere suffering or harm to help narrow down our definition of disease (and thereby our definition of health) to exclude these sorts of cases but still include all those we think merit status as diseases. 

One approach, made famous by Christopher Boorse in the 1970s, the Biostatistical approach, seeks to do away with questions regarding harm altogether. Instead Boorse focuses on giving a definition of what is “normal” and abnormal”. This, it is claimed is the only route to a truly objective and properly naturalistic account of disease. 

According to Boorse’s biostatistical account of disease a disease or pathological condition occurs when an internal state impairs the ability of a person to function normally where normal function refers to the activity of parts of the body or processes in the statistically typical manner to individual survival and reproduction. Here statistically typical manners relates to a particular reference class (e.g. an age, or group or sex, of a species). That is a mouthful but the idea itself is relatively simple. It points out that for a natural grouping of humans by age or sex or a mixture of the two, we can establish what is typical in terms of their bodily functions. This is normal function, or health,  and deviation from it is dysfunction, or disease. For example, we might say that a person has heart disease if their heart is not pumping blood within what we consider the statistically typical manner for someone of their age and sex. Similarly a digestive system has diabetes when it can no longer process sugars within the bounds of what we consider the statistically typical manner for someone of a particular age and sex. 

Boorse’s approach has the advantage of avoiding some of the problem cases raised earlier. Something like childbirth is not a disease, for Boorse, even though it involves suffering in the birthing parent, because it is a part of the normal functioning of the body of a pregnant person. Similarly, Boorse gives us tools to appropriately categorise same sex attraction as not disease or pathology. As mentioned before, same-sex attraction has historically been deemed a mental illness or disease being within the DSM or Diagsnostic and Stastitical Manual of Mental Disorders in some form or another right until the publication of DSM-5 in 2013. Boorse points out that same sex attraction falls into the statistically typical functioning of bodies and so is not pathological, even if it can be extremely harmful to individuals in certain social contexts. 

We will turn to some challenges to Boorse’s account next.

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One major challenge for Boorse’s biostatistical account is determining what counts as normal functioning, and thus what can be considered a dysfunction. Some are skeptical that this can really be done in any principled manner. To quote one skeptic, philosopher of biology Ron Amundson “the partitioning of human variation into the normal versus the abnormal has no firmer footing than the partitioning into races. Diversity of function is a fact of biology.” Essentially he is saying, there is no way to give a mind-independent or objective distinction between cases of apparent disease or dysfunction and simple natural expected variation. Consider, for example, something like acne. We take acne to be a normal part of adolescence and puberty but there is a point at which it is deemed appropriate to seek medical help and perhaps treatement for it. The question is, however, is there any point at which severe acne becomes a disease? Or is it better understood as an extreme of natural human variation? Similarly, to return to the heart disease and diabetes example, at what point do we deem a cut off between normal variation in typical function and dysfunction? How poorly must a heart pump blood to count as not normal? How high blood sugar is too high? There are two moves open to naturalists here. One is to try to give a more principled account of dysfunction. Andrew Wakefield, for example, famously draws on natural selection and the idea of “selected function” to ground dysfunction. Another is to add complexity and a further criteria to the definition—we will get to this shortly.

Before that there is a further worry some raise for Boorse’s approach. Specifically, critics argue that it doesn’t appear to track the practice of scientists and medical doctors. Again, same sex attraction is a key case. Same sex attraction wasn’t, Boorse’s critics argue, removed from the DSM because of some sort of change in our medical knowledge of homosexuality or change in our understanding of the statistically typical functioning of bodies, but because of changes in society concerning values. This, it is said, suggests that there is some important role for values in judgements of disease and pathology. Boorse argues that this is just a mistake, homosexually was never a disease in the first place. It was incorrectly placed in the category and what happened because of poor application of the category of disease, not because disease itself is value laden. This raises a question about how we shoudl think of any definition of disease and its relation to practice. Should it capture all of typical practice by doctors? All of our intuitive ideas of disease? Or should it be at least somewhat revisionary? I won’t try to answer that here, but it looms large in the background.

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As mentioned before, drawing the line between function and malfunction is hard, even if we have a criteria for normalcy. On one common contemporary naturalistic view deals with this by making disease classification a two step process. First we must consider if the behaviour or process in question involves a malfunction or deviation from normal functioning, and then second consider whether it is harmful. If it is both of these things, it is a disease. This allows us to rule out some cases of human suffering which we don’t want to include as diseases such as childlbirth, and also allows for the potential for something which may be harmful or bad for a person in one context but not in another, such as a person with a mild anxiety which only manifests in harm or suffering in extremely stressful contexts. We can claim that such a person does not have a disease unless such stressful contexts are chronically present. 

Whilst this sort of two step naturalistic view gets us out of some challenges, we might still argue that harm is an inherently normative notion. There is no purely objective account of it available. Furthermore, say some, values not only are inherent in our definitions of harm but also in causing what is harmful in the first place.

Here, I am pointing to a very different approach to disease—the constructivist approach to disease. Constructivists say that there is no natural, objectively definable set of human malfunctions which cause disease. Rather, when we assert that something is a disease we are making a judgment about that person undergoing a specific kind of harm that we explain in terms of bodily processes. Those bodily processes are not objectively malfunctioning, rather they are just merely judgemed by us to be unusual or abnormal because of a cultural concept of human nature. In short, there is no naturalistic or scientifically respectable notion of what it is to be a “normal” human and thus we cannot, they argue, ground biology in deviation from that. Rather we must focus on harm. Then, given the challenges outlined at the start, what counts as disease becomes a matter of both context (a state may be harmful in one society and not in another) and also our cultural notions of normalcy. 

This sort of approach seems to well capture cases such as homosexuality. It was in the past considered an abnormal behaviour outside of “human nature” and thus a disease. As our notions of human nature have changed, so too has its status. Importantly, this change is not based in biological facts but values, human nature and thus disease being a social construct. 

The challenge for this approach is that it seems to disconnected from biology and unable to deal with many of the borderline cases. A person that commits a murder, for example, may reasonably be considered to be engaging in beaviour that goes against human  nature as a social kind but it seems a mistake to say they have a disease. Conversely, whilst this view can account for why same sex attraction was in the past viewed as a disease, it doesn’t give us grounds to say that that was objectively a mistake. Which is something I think is important. Again, we seem to have a problem of a criteria that are overly arbitrary.

Neither the constructivist not the biostatistical view or the two step naturalist view are without their problems. They all fail in some cases. Which view do you prefer? 

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