Medical Disorders: From Definition to Nature

There are different philosophical ways of conceptualizing "medical disorders". You could take an essentialistic approach, that medical disorders have necessary and sufficient properties which make them medical disorders (for instance, a demonstrate biological dysfunction). An different approach is a pragmatic one, in which there are no necessary and sufficient criteria, and the characterization of something as a medical disorder depends on various scientific as well as practical considerations (whether the condition is distressing, whether people are seeking help for it, are treatments available, etc.). According to the essentialistic approach, calling something a medical disorder means we are saying something about the nature of the condition. According to the pragmatic approach, calling something a medical disorder does not commit us to any particular view of the nature of the condition (I prefer the pragmatic approach).

There are two other aspects of this discussion:

1) Whether something should be considered a "medical disorder"

2) Whether something should be assessed using the methods of medicine and treated with the tools of medicine (the methods and tools are by themselves evolving & fluid)

From a pragmatic perspective, there is no strict separation between question 1 and 2 because question 2 is itself a consideration for 1. From an essentialistic perspective, the two questions are separate, and the answer to 1 does not determine the answer to 2.

For instance, we could come up with an essentialistic account of disorders in which dysfunctions are defined in such a way as to exclude risk factor conditions. Such an account may exclude hypertension and obesity. In fact, there are many in the medical community who think that hypertension and obesity are not by themselves disorders but risk factors for other disorders.

However, just because a particular definition may exclude hypertension as a "disorder" doesn't mean that hypertension should not be assessed using the methods of medicine and treated with the tools of medicine.

So even if you use an essentialistic definition of disorder (say identificable biological dysfunction), and exclude mental disorders from the category of medical disorders, that does not by itself imply that mental disorders should not be diagnosed or treated medically. 

Whether something should be assessed using the methods of medicine  and treated with the tools of medicine is a highly pragmatic question... it depends on how successful these methods and tools are in achieving goals such as alleviating the associated distress/impairment, improving quality of life, or providing a progressive agenda for medical research, etc.

If a condition can be assessed using the methods of medicine and treated with the tools of medicine, it also doesn't imply that the condition should ONLY be addressed medically; the condition can be addressed using a variety of other non-medical methods and perspectives, especially if those non-medical approaches can demonstrate superiority over medical approaches.

According to the pragmatic approach, if mental disorders are called medical disorders, does it mean we are saying something distinctive about the nature or etiology of these conditions? No, we are not.

Should mental disorders be assessed using the methods of medicine and treated with the tools of medicine? Yes, to the degree to which these methods and tools are successful in achieving desired goals.

Should mental disorders be viewed and addressed through non-medical frameworks? Yes, to the degree to which these non-medical frameworks are successful in achieving desired goals.

If calling mental disorders “medical disorders” does not tell us anything about their nature, then what are mental disorders? The way we currently understand the term, these are behavioral and psychological states that are typically associated with distress, impairment, disability, and harm to self or others, and often seem to violate ‘folk psychological’ expectations of rationality and understandability, and tend to lead to help-seeking behaviors either by the individual or by their community (this is not a necessary or sufficient definition).

Once we have identified such a behavioral and psychological state, then determining the causal nature of the condition is largely a matter of scientific and philosophical inquiry. For scientific method to do its job, it needs to be able to define the phenomena with some degree of reliability. Hence the need for some sort of a labelling and identification method for scientific investigation.

Scientific investigations inform medical practice, but medicine is a practical art, and has its own goals of figuring out ways of making sense of the presentation of patients in clinical settings. Hence, medicine has a need for some sort of labelling and identification method as well. It need not necessarily be the same as the labelling and identified method used for scientific investigation, but to the extent that development of medical treatments relies on scientific investigation, some sharing of nomenclature is unavoidable.

What does science tell us about the nature of mental disorders? So far the picture that emerges from scientific research is one of complexity, in which prototypical metal disorders such as schizophrenia and depression do not have single causes, but appear to have a wide array of biological, psychological, and social risk factors, and these risk factors interact with each other in unknown ways.

Whether mental disorders are considered medical disorders or not (depending on the definition of “medical disorder” used), their causal nature is not and cannot be determined by the definition and by a priori conceptual considerations. That is largely an empirical question.

Do mental disorders have physical causes? Well, it depends on what we mean by cause. Currently we think of cause as similar to a risk factor, as something that influences the risk or probability of developing the condition in question (for instance, smoking changes the probability of developing lung cancer). These risk factors are often neither sensitive nor specific (not all individuals with lung cancer smoke; not all smokers develop lung cancer). Non-sensitive, non-specific risk factors don’t help identify or diagnose the condition, but that doesn’t mean that their causal influence is not real. In psychiatry we have a lot of such non-sensitive, non-specific risk factors, which means that although their causal influence may very well be real (which is a matter for science to determine), they are not helpful in the clinical task of diagnosing an individual patient.

Some people think of cause as a single entity (or a small set of entities) which should be necessary for the development of a condition, for instance, Mycobacterium tuberculosis is necessary for the development of Tuberculosis. That is a popular, common-sense understanding of cause, but that is not necessarily the notion of cause employed by physicians and scientists. If we were to restrict ourselves to this narrow definition of cause, then many entities in medicine would have no cause at all, even though they are recognized to have many risk factors.