Classification in Biology, Medicine, and Psychiatry

 

Classification in Biology, Medicine, and Psychiatry

I was a double major in college – biology and chemistry. Anyone with similar experience who has done fieldwork in zoology, botany, or associated systems disciplines like ecology is aware of various forms of biological classification. I spent months doing population surveys of plants, aquatic invertebrates, and plankton in undergrad courses and working on water quality surveys for the southern tributaries of Lake Superior.  In the winter, a friend and I would go out on the ice in various locations, chop a hole in the ice, and pump about 80 gallons water through a plankton net – and then carefully take that concentrated sample back to the lab and count plankton species under a microscope. It was painstaking work – but the payoff was a much greater knowledge of the life forms around you.  The lakes, streams, and rivers, and even the ground you were standing on is teeming with life.  Hundreds of species that were unknown until you took those courses and learned how to collect and classify them.

All of that classification was done using a Linnean binary classification system – genus followed by species. As an example, Loblolly pine is Pinus taeda.  Douglas fir is Pseudotsuga menziesii. The Douglas fir example is given because it is not a true fir tree (genus Abies) despite the common name.  The difference is based on morphological characteristics although the entire genome was characterized in 2017. Both the common and scientific names illustrate how species are named.  The common name was after David Douglas a Scottish botanist who described it and the species name after Archibald Menzies – a Scottish physician and naturalist.

Other physicians have been involved in the taxonomy of both human diseases and biological species most notably Carl Linnaeus (1707-1778) – a Swedish physician who is credited with founding the binomial nomenclature used in all modern taxonomy.  He also recognized the necessity of organizing illnesses so that physicians could know they were discussing similar problems. By 1746 he had organized them into nine classes – critici, phlogistici, doloritici, mentales, privatii, spastici, deformans, evacuatorii, and chrirurgia.  Linnaeus was trained as a physician and got his doctorate degree in 1735, but worked as a physician intermittently and for a short period of time until 1741 when he became a professor of botany and theoretical medicine.  

Linnaeus also focused on a species diagnosis rather than a description, meaning features that could clearly distinguish one taxon from another. He went as far as saying the diagnosis should not exceed 12 words and should include previous references and diagrams (6). According to the same reference, the concept of species diagnosis is included in modern nomenclature for species as: “a statement of that which in the opinion of its author distinguishes the taxon from others.” (p. 1090).

Linnaeus taught medical students a course in the diagnosis of disease and in 1759 published a book - Genera Morborum (Varieties of Disease).  He described 11 classes of disorders, 37 orders and 327 genera.  Mental disorders (Mentales) were divided into 3 orders and 25 genera (7). Inspecting the list from that reference suggests that delirium, mania, melancholia, hypochondriasis, anxiety, sleep, and appetitive disorders were all included.  Vertigo was also included and today is considered a neurological or otolaryngological diagnosis.  The overall tenor of reference 7 is that the various systems devised by 17^th and 18^th century physicians would never attain the level of certainty as the biological taxonomy used in natural history that we now know is also controversial.

That brings me back to the problem of biological classification – specifically speciation. That has been a predominate area of study in biology since Darwin and it is not without controversy despite the broad use of these methods in all of biology and science. What is equally interesting is that as far as I know there have been no direct comparisons to medicine and psychiatry.

Let me start by touching on the controversies of speciation from a biological standpoint.  I qualify these remarks by saying my training was at the undergraduate level and all of what I say here is based on recent readings.  I am very interested in hearing from professional biologists on this topic and so far have not been able to get any email responses. My overriding hypotheses are that the same mechanisms leading to speciation controversy in biology may be responsible for classification controversy in medicine and psychiatry.

Coyne and Orr (1) break down speciation into three phases.  The first phase began with Darwin and they point out that he had more to say about changes within species than the origin of new species.  Natural selection was seen as the most important force. The second phase began in about 1935 and was also known as the Modern Synthesis.   It was also marked by a critique of the species concept by Dobzhansky a noted evolutionary biologist.  Reproductive isolating mechanisms were stressed as a necessary cause of speciation. Ernst Mayr another noted evolutionary biologist came up with the biological species concept (BSC).  He defined species as interbreeding populations that are reproductively and geographically isolated from one another.  The third phase started in the 1980s. Coyne and Orr suggest that “more work on speciation has been performed in the past two decades than the entire period from 1859 to1980.”   They speculate that this explosion of work was due to several factors including the new tools of molecular genetics, more extensive use of mathematical models, a new emphasis on ecology, and a use of comparative studies.  The old hypotheses about speciation were re-examined and many new concepts were introduced (in addition to the BSC).  They list nine possibilities grouped as based on interbreeding, genetic or phenotype cohesion, evolutionary cohesion, and evolutionary history (p. 27).

Coyne and Orr described how the species concept was validated over the years.  First, arguments from common sense.  That is that anyone can see clusters of species and recognize they are real. This same phenomenon occurs with physical and psychiatric illnesses.  A second stronger argument is that there is concordance between folk and scientific species.  In this case researchers will look at the species in a given area and see if it is separated out and recognized by local people as being a unique cluster of traits.  That has also been referred to as folk taxonomy.  The concordance is typically high, and I suggest that the same type of concordance experiment is not only possible in medicine – it may have been done using the disease concept (2,3). And finally statistical identification of clusters. This has been done with both medical and psychiatric diagnoses to examine diagnostic features and also to determine if they separate different clusters adequately enough from one another.

The authors carefully explain the exceptions to the various species concept and settle on their own version of the BSC as the more viable one. But even the modern-day species concept is a problem because it does not clearly define all cases.  Several authors refer to it as the “species problem” and there is ongoing controversy in the literature. At the extreme there have been suggestions that the idea of species stems from a limitation of human cognition (we must lump things into categories) or there is a biological continuum that we are marking up arbitrarily.  Any reader of this blog realizes that these are frequent arguments made against psychiatric diagnoses and by extension other complex polygenic medical conditions.  Keep in mind that as far as I know all biology majors working on taxonomy in the past 50 years use the same binary system of classification that I used in college.

To their credit the authors propose how the species concept is useful and they come up with the following observation most biologists want an operational classifier that allows for systematic classification, describes what is seen in nature, helps develop an understanding about how things occur in nature, is consistent with evolutionary history, and applies to most organisms. In other words, it is not very different from what physicians expect diagnostic classifiers to do.  They realize that these are imperfect complex, multidimensional classifiers that are nonetheless useful for daily work and can be fine-tuned for improvements in the individual case.

That is what I am working on so far. I think I have demonstrated how biological classification even using all available methods and directly observable data is difficult if not impossible in many cases. The same can be said about medical diagnoses. That is because both the medical diagnoses and binary species designations are complex, multidimensional variables rather than basic physical structures. It does not mean that groupings in biology do not exist.  The key questions for my additional focus will be on the underlying mechanisms.  I have already described stochastics as a basic biological mechanism introducing some degree of uncertainty into biological systems – but I am sure there are many more.  In this era of proposed alternate diagnostic systems for mental disorders (Research Domain Criteria (RDoC), The Hierarchical Taxonomy Of Psychopathology (HiTOP), etc) – my reading so far suggests that there has been very little input from biological sciences. In most cases it seems like just a reshuffling of existing theory and measurement. My hypothesis going forward is that biological theory has a lot more to offer.

 

George Dawson, MD, DFAPA

 

References:

 

1:  Coyne JA, Orr HA.  Speciation.  Sunderland, MA Sinauer and Associates, 2004: 1-82.

2:   Tikkinen KA, Leinonen JS, Guyatt GH, Ebrahim S, Järvinen TL. What is a disease? Perspectives of the public, health professionals and legislators. BMJ open. 2012 Jan 1;2(6):e001632.

3:  Tikkinen KAO, Rutanen J, Frances A, Perry BL, Dennis BB, Agarwal A, Maqbool A, Ebrahim S, Leinonen JS, Järvinen TLN, Guyatt GH. Public, health professional and legislator perspectives on the concept of psychiatric disease: a population-based survey. BMJ Open. 2019 Jun 4;9(6):e024265. doi: 10.1136/bmjopen-2018-024265. PMID: 31167856; PMCID: PMC6561450.

4:  Hey J.  Genes, categories, and species. NY, NY. Oxford University Press, 2001.

5:  Broberg G.  The man who organized nature.  Princeton, NJ. Princeton University Press, 2023; p. 221.

6:  Renner SS. A Return to Linnaeus's Focus on Diagnosis, Not Description: The Use of DNA Characters in the Formal Naming of Species. Syst Biol. 2016 Nov;65(6):1085-1095. doi: 10.1093/sysbio/syw032. Epub 2016 May 4. PMID: 27146045.

7: Munsche H, Whitaker HA. Eighteenth century classification of mental illness: Linnaeus, de Sauvages, Vogel, and Cullen. Cogn Behav Neurol. 2012 Dec;25(4):224-39. doi: 10.1097/WNN.0b013e31827de594. PMID: 23277141.

 

Graphics Credit:

Stonefly drawing by Carpenter, George H. (George Herbert), 1865-1939.  Public domain per Wikimedia Commons.  Genus is Plecoptera and it was one of the many species I studied in freshwater streams of Wisconsin and Michigan as an undergrad.  Click on the graphic for details. 

Irrational American Gun Landscape Gets Worse….

The Supreme Court voted 6-3 to lift the ban on bump stocks yesterday (on June 14, 2024). The bump stock is a device that allows a shooter to depress the trigger of a semiautomatic rifle once.  After the initial firing the recoil energy of the firearm is used to bring the trigger back against the trigger finger for repeated firing without a subsequent trigger pull.  The result is a very high rate of fire with various quotes of 800 rounds per minute.  The limiting factor is rounds in the magazine and a standard magazine is 30 rounds with some states having lower limits or no limits.  

The majority decision was done by the Republican appointed justices (Roberts, Alito, Gorsuch, Kavanaugh, and Barrett), who used a series of rationalizations to show that in their opinion the bump stock does not convert a semiautomatic weapon to a machine gun as defined by the National Firearms Act of 1934.  Note that the majority opinion uses graphics (Figures 1-6) from the Firearms Policy Foundation - an organization that fights gun control laws (see reference 2 and their web site).  The dissenting opinion by Justice Sotomayor in the final few pages points out the inconsistencies in the majority opinion.  

Both court opinions include the precipitant for the bump stock ban – a 2017 Las Vegas shooting where the perpetrator was able to fire over 1,058 rounds from a hotel room into a crowd at a music festival killing 60 people and wounding 413.  An additional 454 people were injured in the ensuing panic. The gunfire occurred from 10:05 to 10:15 PM.  It is the deadliest mass shooting in the country that holds the record for mass shootings.  From the perspective of bump stocks, the Las Vegas shooter used 14 AR-15 (.223 cal) semiautomatic rifles and 8 AR-10 (.308 cal) semiautomatic rifles.  All of the AR-15s were fitted with bump stocks and 100 round magazines.  None of the AR-10s were fitted with bump stocks and 5 of 8 had 25 round magazines.  The remaining three AR-10s had no magazines. The AR-15s had a potential capacity of  1400 rounds that could have been discharged with a bump stock. The relevant factors from this list is that magazine capacity rather than firing rate is the major limiting factor in the total number of rounds that can be discharged and the shooter overcame that limitation by using more firearms with bump stocks. Only 15 states ban or restrict large capacity magazines.

There are various opinions in the media about how a bump stock ban originated in the Trump administration. The politics is interesting because the precipitating event was so egregious that the National Rifle Association supported restrictions on bump stocks.  I can find no action by the Trump administration other than encouraging the Bureau of Alcohol, Tobacco, and Firearms (ATF) to consider rule changes and in fact this report suggests there was a memo circulated with the usual “guns don’t kill people” message.  The Supreme Court refers to the ATF rule changes but also makes one reference to Trump.  Unless I missed something it seems clear that he did very little on the issue.

At the end of the day – we have a typical party line vote supporting gun extremism.  I don’t care who you are – the only reason you need a bump stock is to kill large numbers of people.  A bump stock is not useful for hunting or target shooting.  It converts a weapon that is already a military weapon (semi-automatic rifle) to what is essentially a fully automatic rifle. Justice Sotomayor’s opinion also includes the original reason for the machine gun ban and that was to keep these weapons out of the hands of gangsters.  Two of the typical gun extremist arguments against even minimal forms of gun control are:  “We already have enough gun laws on the books and they are not enforced” and “If we have more gun control laws only the criminals will have guns.”  They make these arguments while continuing to deregulate guns, make gun regulations harder to enforce, and make guns even more widely accessible either by Republican legislators or judges.

A second development on firearms was a recently released report by the CDC on the accessibility of firearms by children.  This is a timely study because of the April 2024 Michigan court case against a couple whose son shot and killed 4 students at his high school.  In that case the couple was found guilty of involuntary manslaughter and sentenced to 10 years in prison because their son used an unsecure handgun and they did not attend to behavior suggesting he could become violent. At the time of the shooting Michigan did not have a statute about securing firearms at home and that law was passed during the first prosecution of the parents. It was widely hailed as a warning to parents about securing firearms at home.

The CDC report was based on a Behavioral Risk Factor Surveillance System module administered in 8 states (AK, CA, MN NV, NM, NC, OH, and OK)  in 2021–2022.  The survey was administered by land line telephone calls. The nonresponse rate ranged from 3.5% to 12.8% by state.  The prevalence of firearms kept “in or around the home” was 18.4% (CA) to 50.6% (AK).  The general figure from Gallup is in the high 40%.  In 19.5% (MN) to 43.8% (NC) the firearm was stored loaded. Half of those reporting storing a loaded firearm said it was unlocked.  25.2% (OH) to 41.4% (AK) of those reporting storing an unlocked loaded firearm also reported children less than the age of 17 in the home.  For adults 65 years of age or older 58.5% (NM) to 72.5% (OK) of those with firearms had them stored unlocked.  The authors list the usual limitations of telephone self-report surveys but do not comment on cultural or political factors like the belief of some gun owners that the government is coming for their guns.  

The authors conclude that unlocked firearms may place children and other vulnerable populations at risk.  There is a higher suicide risk in the elderly.  It also illustrates how common the scenario is that led to the conviction of the parents for their son being a mass shooter. A secondary consideration of those convictions was a warning to parents that firearms at home need to be secured to prevent them from similar risks. As I commented at the time, that is a very inefficient approach to a problem that could be addressed at the population wide level. It is in effect, one political party putting parents at risk to continue saturating the population with firearms. And now we know it may be  about four in ten parents who store unlocked, loaded firearms, with children in the home.

To me, mass shootings are a function of:

- mass availability of high-capacity and rapid-fire firearms - both rifles and handguns

- gun extremism translated into effects at every level

- cultural effects - the disgruntled employee/student/etc as mass shooter has been an American meme for 50 years...

The Republican Party and their judicial appointees essentially control two of those three variables.  They are a party with no good ideas but they know how to get votes by stimulating excessive emotion around issues like firearms and abortion.  Their current approach to firearms is to place large part of the population at chronic risk with an arbitrary interpretation of the Second Amendment that they think that they can use to get votes. The basis for their gun extremist view, including the current Supreme Court decision is based on false premises rather than rational thought or legal precedent.  Americans generally don’t expect much from political parties and now they can expect the same from a highly partisan Supreme Court.    

George Dawson, MD, DFAPA

 

Supplementary:

I frequently talk about gun extremism on this blog and decided to attach a checklist of what I consider gun extremism to be.  Basically it is a marked divergence with common sense gun laws from the 1970s and earlier (see Tombstone ordinance from 1881). From a political standpoint it is clearly a political maneuver to excite and agitate people and get them to vote for a particular political party.  Like all of the so-called hot button issues it is an exercise in rhetoric and conspiracy theories that has unfortunately led to historic levels of gun violence in the US when compared with high income and low and medium income countries around the world.    

 

Gun extremism checklist:

☐  Advance “stand your ground” and “castle doctrine” laws.

☐  Eliminate bans on handguns

☐  Eliminate bans on assault weapons

☐  Minimize the characterization of “assault weapons” or military style weapons because they are not fully automatic weapons

☐  Eliminate bans on large capacity magazines

☐  Eliminate waiting periods

☐  Eliminate bans on public carry of guns

☐  Eliminate the need for permits to purchase handguns and/or carry them openly or as concealed weapons

☐  Eliminate gun-free locations (ie. places of worship, public transportation, healthcare facilities, public buildings)

☐  Eliminate bans on self-manufacturing of firearms

☐  Eliminate laws on age limits to firearm purchase and possession

☐  Eliminate laws on age limits for handgun and ammunition purchase

☐  Eliminate bans on gun accessories like bump stocks and pistol grip extensions

☐  Eliminate laws on “cannot issue” firearms to certain purchasers

☐  Eliminate gun purchase bans for perpetrators of domestic violence

☐  Eliminate gun purchase bans for convicted felons

References:

1:  Friar NW, Merrill-Francis M, Parker EM, Siordia C, Simon TR. Firearm Storage Behaviors — Behavioral Risk Factor Surveillance System, Eight States, 2021–2022. MMWR Morb Mortal Wkly Rep 2024;73:523–528. DOI: http://dx.doi.org/10.15585/mmwr.mm7323a1

2:  Lithwick D, Stern MJ. The Group Helping the Supreme Court Rewrite America’s Gun Laws Is Worse Than the NRA.  Slate June 15, 2024.  https://slate.com/news-and-politics/2024/06/supreme-court-nra-gun-laws-bump-stocks.html

3:  McClellan C, Tekin E. Stand your ground laws, homicides, and injuries. Journal of human resources. 2017 Jul 1;52(3):621-53.

4:  Rosenthal L. The limits of Second Amendment originalism and the constitutional case for gun control. Wash. UL Rev.. 2014;92:1187.

5:  Rowh A, Zwald M, Fowler K, Jack S, Siordia C, Walters J. Emergency Medical Services Encounters for Firearm Injuries — 858 Counties, United States, January 2019–September 2023. MMWR Morb Mortal Wkly Rep 2024;73:551–557. DOI: http://dx.doi.org/10.15585/mmwr.mm7324a3

6:  Andrade EG, Hoofnagle MH, Kaufman E, Seamon MJ, Pah AR, Morrison CN. Firearm laws and illegal firearm flow between US states. J Trauma Acute Care Surg. 2020 Jun;88(6):752-759. doi: 10.1097/TA.0000000000002642. PMID: 32102044; PMCID: PMC7799862.

"States with stricter firearm legislation are negatively impacted by states with weaker regulations, as crime guns flow from out-of-state."

 

Graphics Credit:

From Wikimedia Commons per the posted Creative Commons licensing agreement. Click on the graphic for all details including author, color coding, and specific CC license.

Philosophy of psychiatry: rhetoric or reality?

 

“If you laid all philosophers end-to-end it would be a good thing.”  Anonymous philosopher lecturing medical students somewhere in the Midwest in the 1980s. 

 

This post is a partial commentary on a paper about the philosophy of psychiatry (1) that was recently published.  Since I am not a philosopher and do not aspire to be one – I thank the authors for commenting on what they believe the key issues and limitations are. Over the years I have written about philosophical conjecture about psychiatry and consider much of it to be serious overreach. This paper will allow me to make some general observations.  The authors in this case have all published previous work on the subject and given the number of co-authors this is considered a state-of-the art review.  The review is open access and can be read at the link in the reference.

In their introduction the authors – consider metaphysical, epistemological, and ethical issues to be critical at the grey zone between medicine and philosophy.  They mention Karl Jaspers as a seminal figure in the field but emphasize their focus in the paper will be on conceptual competence defined as: “the transformative awareness of the ways by which background conceptual assumptions held by clinicians, patients, and society influence and shape aspects of clinical care” (2).  To their credit they explicitly comment on controversies about what the parameters of good philosophy are and whether progress is made over time.

Their first point is on the boundaries of disorder.  They make the usual observations about Kraepelinian and neo-Kraepelinian and conclude that “neo-Kraepelinians (NKs) claimed that precisely defined diagnostic criteria could be used to discover the specific biological causes of psychiatric syndromes and establish psychiatry as a branch of medicine.”  There is plenty of evidence that the NKs were much more sophisticated than that.  From one of their references (3): 

“The medical model is not based on any assumptions about etiology. It can accept social and psychological causes as well as physical and chemical events.  It can accept single causes or multiple causes.  It can even be applied when the etiology is unknown as in many clinical investigations.”

Guze specifies in several places that the diagnosis is for describing what is known about the patient and treatment planning. He suggests that medicine and psychiatry may evolve to provide more information on pathophysiology and testing but does not link it to diagnostic criteria apart from how it might be studied. He does not suggest that biological causes are necessary to establish psychiatry as a branch of medicine – his entire monograph is about why psychiatry is already a branch of medicine.

The next transition is to Insel and the RDoC.  The criticism seems to be that Insel was criticizing biological psychiatry but I doubt that any biological psychiatrist would see translational neuroscience as being inconsistent with a brain and biological centric psychiatry. The field is described as “lurching from one model to another”.  Excluding homosexuality as a diagnosis is given as a notable example of diagnostic controversy rather than psychiatry (specifically Spitzer) getting it right and leading society in general by about 40 years.  There are still plenty of people who have not caught up.

The first main section of their paper is the nature of mental illnesses.  They define strong naturalism as the factual and value free description of a disorder like what occurs in the natural sciences. They equate biological psychiatry with neurobiological dysfunction – even though those psychiatrists clearly had a much more sophisticated view of psychopathology.  I have quoted their reference to Guze above – here is an additional quote from prominent biological psychiatrists of the 20^th century:

“It should be emphasized…that the demonstration of…[a catecholamine] abnormality would not necessarily imply a genetic or constitutional, rather than an environmental or psychological, etiology of depression…it is equally conceivable that early experiences of the infant or child may cause enduring biochemical changes and that these may predispose some individuals to depressions in adulthood…[and] any comprehensive formulation of the physiology of affective state will have to include many other concomitant biochemical, physiological, and psychological factors.” (4)

That sounds like pluralism rather than naturalism to me.  There are several additional factors that suggest that the idea of strong naturalism is an exaggeration of the position of late 20^th century biological psychiatrists.  Some of those factors include: the concept of heterogeneity in diagnostic categories was widely known at the time, endophenotyping was introduced in 1966 as a purely biological concept (5) that was later applied to medicine and psychiatry (6).  Clinical trialists were certainly aware of heterogeneity and significant problems with recruiting patients into studies based on severity and placebo response.  The general comparison to medical conditions where a significant portion were idiopathic and had speculative pathogenesis and to this day are still diagnosed based on clinical description is an additional factor.  Any intern on medicine or surgery knows pathophysiology and the suggested mechanism of action of medications is typically speculative and no two patients with the same diagnosis are exactly alike.  A key concept in training is that physicians are required to recognize that pattern and make the necessary adaptations.

The authors introduce the definition of strong normativism as basically “no natural, objectively describable set of biological processes that we can characterize as “dysfunctional”, and hence disorder attributions are thoroughly value-laden.”  They do not elaborate – but this definition is clearly counter to the experience of any physician who has treated life threatening or severe illnesses.

Szasz is introduced at that point because of his suggestion that mental illnesses do not exist but rather represent “judgments of deviance based on sociocultural norms”.  They suggest that he is both a strong normativist and a strong naturalist rather than just being wrong.  Szasz’s philosophy (if that is what it was) fails several tests, but for the purpose of this post is probably the best example of controlling the premise rhetoric to prove a point.  The Szasz definition of disease as actual observable pathology allows him to trivialize any condition not meeting that criterion (and there are probably more outside of psychiatry than within) and call it a value judgment.  That is not consistent with diagnostic systems present before him or what historical neuropathologists thought (7).

What follows is a section on the naturalist-normativist debate including a table of the contrasting points. The basic problem with this dichotomy is that the normativist position as described by the authors is such a caricature when compared with medical and psychiatric training that it really cannot be seen as a viable position by anyone but Szasz.  They produce a couple of examples of hybrid positions as though they have never been considered in the past.  The description of Wakefield’s suggestion that dysfunction that is harmful to the individual is required for disorder, but since depression is an evolutionary response to adversity it is not dysfunction.  That ignores empirical research that suggests that it can be both as well as the problems associated with speculation in evolutionary psychology. The discussion of values in the normative model leaves out a lot and ignores psychiatric training. If the goal is to inform psychiatric practice by this kind of debate there are better ways to go. Psychiatrists walk into the room with a patient and their goal is to understand that patient well and treat that patient well. That involves communication skill, developing a therapeutic alliance, therapeutic neutrality, and providing the patient with enough information so that they can provide informed consent.  That interaction is both scientifically and professionally informed.

The next concept the authors discuss is essentialism or the idea that naturally occurring kinds have an evident essence. They acknowledge that when it comes to medical disorders straightforward classification is generally problematic but for some reason it is more problematic for psychiatry. They suggest that:

“If psychiatric classifications such as the DSM and the ICD were demarcating natural kinds, we would expect each diagnosis to correspond to an entity that exists in the structure of the world, independent of human interests.”

That quote misses the mark at a couple of levels.  First, a classification system is really not a diagnosis. It is more of a hypothesis and general locator (8). The diagnosis takes additional information including some of the validators that they minimize in this section. Second, in looking at these features it is obvious that many of the big ones – like mania “exist in the world independent of human interests.”  They have after all been described since ancient times across multiple diagnostic systems – long before there were psychiatrists.  The same is true of melancholia and several other disorders. Granted – there was no DSM back then but I cannot think of better evidence that there are natural kinds by this definition that have been updated. Third, it should be obvious that many disorders are clearly there for research purposes and this is evidenced by the fact that only about 50% of the diagnoses are used on a clinical basis and many psychiatrists attest to the fact that they doubt a single case of specific disorders exist (9,10).  Finally, essentialism in biology became a casualty of evolution.  Prior to Darwin, Linnaeus suggested that species were distinct and unchanging entities created by God.  That is an essentialist position. Evolutionary theory changed all of that because species change based on individual variation and new species occur (11). 

Whenever I read about the philosophical concepts behind what constitutes psychiatric illness and classification – I am always left considering why philosophy is prioritized over biology.  Medicine is after all firmly rooted in human biology.  There is no better evidence than the biochemistry, anatomy, and physiology courses taken in medical school basic science.  Biology provides a framework for both hierarchical organization as well as individual classification of diseases including mental disorders (see lead graphic). Modern taxonomic classifications of both date back to the mid -18^th century.

A critical question is whether biological classification has advanced to the point where it is not controversial and purely scientific.  The short answer is no. There is ample evidence that the taxonomy of living organisms is problematic and there are ongoing controversies over the past 50 years.  Although species is a fundamental organizational concept in the field of biology that has not prevented the proliferation of up to 24 different species concepts in recent times (12).  Why would medicine be expected to have a more clearly defined classification system than biology?

Rather than comment on the remaining sections that I am sure that I also have problems with – I am going to introduce and idea that I have not seen written about anywhere.  If you read this an think I am wrong please let me know and send references.  That idea is the application of biological theory to psychiatry. Medicine and psychiatry are after all firmly based in human biology and human biology is a subset of biology in general.  When you attend medical school and complete all the basic science training this basic fact is explicit. There is not much discussion of other organisms unless they happen to be pathogens.  There is also not much discussion of the levels of organization in human biology and the implications that has for medicine.

What does the tremendous complexity of biology have to do with psychiatry? It is evident that various mechanisms make it very difficult to classify biological organisms.  That has resulted in many species concepts and that array of concepts has complicate taxonomy at a time when the biodiversity of the planet remains inadequately characterized. Psychiatry is operating only in one species by the same mechanisms that complicate biology at all levels also complicate biology.  To the purpose of this essay the critical question is why they currently seem less important than the increasing presence of philosophy in psychiatry. Frequently the justification seems to be the old quote about “carving nature at the joints.”  Does that mean we philosophize about it and maintain endless arguments?  Or does it mean we consider that human beings and their mental disorders are based in human biology and try to make sense of it by studying biological principles.  And by biological principles – I don’t mean the typical jargon of biological psychiatry used by critics. I mean theoretical biology practiced by biologists.      

I want to touch on just two concepts from biology that have implications for psychiatric controversies.  The first are the classification systems in biology and the second is stochastics.  There are any number of authors offering descriptions about how psychiatry has evolved in the last 200 years. That generally tracing the origins back to 19^th century European schools of thought and bringing those threads forward.  The focus is generally on nosology including diagnostic systems, treatment settings, and how treatments evolved.  The brief discussion of biological classification here touches on a large literature that has been ignored by medicine and psychiatry.  In the debate of categorical versus dimensional diagnoses and the various philosophical labels a significant number of biological classifiers have been left out.

If I am correct what might have caused this significant omission? First, the focus of medicine has been description based on clinical findings.  I have used this characterization previously:

"For several thousand years physicians have recorded observations and studies about their patients.  In the accumulating facts they have recognized patterns of disordered bodily functions and structures as well as forms of mental aberration.  When such categories were sufficiently distinctive, they were termed diseases and given specific names. “

DeGowan and DeGowan, Bedside Diagnostic Examination. 1976, p 1

That has been the historical and primary focus of medicine. Interest in pathogenesis happened in the 19^th century but even then, there were conditions that that escaped that classification.  There has been progress there are still many conditions with no clear pathophysiology and even fewer medications where the mechanism of action is known. One of the primary reasons is that medicine has been based on reductionist biology and even though advances have been made it seems to have reached its limit. What do I mean by reductionist biology?  Simply put it means breaking down complex systems to component parts and studying those parts independently.  In current jargon it has also been referred to as a bottom-up approach.  Second – biological psychiatry is biological in the reductive scientific sense and it needs to be biological in the integrative sense. All biology is not reductive (17,18) – but much of the philosophy I have read seems to think so.  Reductive approaches have led to discrete research programs that produce highly speculative connections to psychiatric disorders. We end up with biological psychiatry as neurochemistry -> neuroendocrinology -> neuroimaging -> genomes, connectomes, proteomes, transcriptomes, metabolomes, etc without any clear underlying connection to all human biology.  Systems biology or network medicine approaches have been used on only a partial basis so far.  Third, rather than make a truly biological connection the field seems to have been sidetracked by philosophy.  Much of that philosophy has been around for 50 years or more and seems satisfied with the role of asking questions and never really providing much of an answer.  Much of the philosophy is vague and untestable.  A secondary role seems to be the criticism of psychiatry with a dependence more on political rhetoric than reality.

Conclusion:

When philosophers criticize medicine and psychiatry, they frequently use the term constructs.  From a rhetorical perspective not, all constructs are alike.  In medicine and biology there needs to be at least some real-world observable basis.  

Rather than strong arguments for philosophy in psychiatry – the authors have argued strongly. I have tried to elucidate the rhetoric involved since my observation is that is the nature of most philosophical arguments directed at psychiatry.  The curious aspect is that most people do not even consider this when reading philosophers commenting on psychiatry.  I sent one of my papers to a friend who has been a psychiatrist as long as I have and he told me that he never considered it an area for analysis. I hope that some of the comments here are useful in considering these arguments and why they should not be blindly accepted.

It seems that in all the philosophical criticism and discussion of psychiatry, van Fraassen's empirical adequacy has been ignored (16, 17).  The reasons for that may be less than obvious.  Van Frassen basically states that an empirically adequate model is just that – it is not a comment on the truth of existence or not.  There is a question of whether the model must be based on direct observation.  The criteria for mental disorders require reporting subjective states that are not directly observable. Van Fraassen’s theory includes the outcomes of experiments and isomorphic models – both of which apply to work in psychiatric nosology. The lack of comment on Van Fraasen’s approach is critical because it reflects how psychiatrists are actually trained and directly counters arguments about positivism and realism. Some references suggest that what appear to be diametrically opposed arguments in philosophy are just sustained with no resolution and that is a significant limiting factor when considering what psychiatrists need to know.           

Not all biology is reductionist and not all philosophy is useful.  Empirical adequacy and biological complexity are the future of psychiatry.

 

George Dawson, MD, DFAPA

 

References:

1:  Stein DJ, Nielsen K, Hartford A, Gagné-Julien AM, Glackin S, Friston K, Maj M, Zachar P, Aftab A. Philosophy of psychiatry: theoretical advances and clinical implications. World Psychiatry. 2024 Jun;23(2):215-232. doi: 10.1002/wps.21194. PMID: 38727058; PMCID: PMC11083904.

2:  Aftab A, Waterman GS. Conceptual competence in psychiatry: recommendations for education and training. Acad Psychiatry 2021;45:203-9.

3: Guze SB. Why psychiatry is a branch of medicine. Oxford: Oxford University Press, 1992. p. 38.

4:  Schildkraut JJ, Kety SS. Biogenic amines and emotion. Science. 1967;156 (3771):21-37.

5:  John B, Lewis KR. Chromosome variability and geographic distribution in insects. Science. 1966 May 6;152(3723):711-21. doi: 10.1126/science.152.3723.711. PMID: 17797432.

6:  McGuffin P, Farmer A, Gottesman II. Is there really a split in schizophrenia? The genetic evidence. Br J Psychiatry. 1987 May;150:581-92. doi: 10.1192/bjp.150.5.581. PMID: 3307978.

7:  Pies R.  Did Szasz Misunderstand Virchow’s Concept of disease? Psychiatric Times. Feb 21, 2024.  https://www.psychiatrictimes.com/view/did-szasz-misunderstand-virchow-s-concept-of-disease

8:  Kendler KS. The Phenomenology of Major Depression and the Representativeness and Nature of DSM Criteria. Am J Psychiatry. 2016 Aug 1;173(8):771-80. doi: 10.1176/appi.ajp.2016.15121509. Epub 2016 May 3. PMID: 27138588.

9:  Munk-Jørgensen P, Najarraq Lund M, Bertelsen A. Use of ICD-10 diagnoses in Danish psychiatric hospital-based services in 2001-2007. World Psychiatry. 2010 Oct;9(3):183-4. doi: 10.1002/j.2051-5545.2010.tb00307.x. PMID: 20975866; PMCID: PMC2948730. 

10:  Müssigbrodt H, Michels R, Malchow CP, Dilling H, Munk-Jørgensen P, Bertelsen A. Use of the ICD-10 classification in psychiatry: an international survey. Psychopathology. 2000 Mar-Apr;33(2):94-9. doi: 10.1159/000029127. PMID: 10705253

11:  Hey J.  Genes, categories, and species. NY, NY. Oxford University Press, 2001: p 60-61.

12:  De Queiroz K. Ernst Mayr and the modern concept of species. Proceedings of the National Academy of Sciences. 2005 May 3;102(suppl_1):6600-7.

13:  Mayr E. Biological classification: toward a synthesis of opposing methodologies. Science. 1981 Oct 30;214(4520):510-6. doi: 10.1126/science.214.4520.510.

14:  Mayr E. Biology is not postage stamp collecting. Interview by R. Lewin. Science. 1982 May 14;216(4547):718-20. doi: 10.1126/science.7079730. PMID: 7079730.

15:  Ho CC, Lau SK, Woo PC. Romance of the three domains: how cladistics transformed the classification of cellular organisms. Protein Cell. 2013 Sep;4(9):664-76. doi: 10.1007/s13238-013-3050-9. Epub 2013 Jul 19.

16:  Van Fraassen.  BC.  The Empirical Stance.  New Haven: Yale University Press, 2002.

17:  Monton, Bradley and Chad Mohler, "Constructive Empiricism", The Stanford Encyclopedia of Philosophy (Summer 2021 Edition), Edward N. Zalta (ed.), URL = <https://plato.stanford.edu/archives/sum2021/entries/constructive-empiricism/>.First published Wed Oct 1, 2008; substantive revision Tue Apr 13, 2021

18:  Loscalzo J, Kohane I, Barabasi AL. Human disease classification in the postgenomic era: a complex systems approach to human pathobiology. Mol Syst Biol. 2007;3:124. doi: 10.1038/msb4100163. Epub 2007 Jul 10. PMID: 17625512; PMCID: PMC1948102.

19:  Van Regenmortel MH. Reductionism and complexity in molecular biology. Scientists now have the tools to unravel biological and overcome the limitations of reductionism. EMBO Rep. 2004 Nov;5(11):1016-20. doi: 10.1038/sj.embor.7400284. PMID: 15520799; PMCID: PMC1299179.

 

Dedication:  This post is dedicated to my undergraduate biology Professors at Northland College including Lee Stadnyk, Richard Verch, John Brennan, and Mallanpali Rao. I spent many months studying the comparative anatomy and physiology of invertebrates and the taxonomy and population dynamics of sphagnum moss plant species, aquatic invertebrates, and freshwater plankton with these professors and they were the best.  I also had the pleasure of working on Loblolly Pine (Pinus taeda) and Douglas Fir (Pseudotsuga menziesii) species in Don Durzan’s lab at the Institute of Paper Chemistry. Experience in biology is a grounding in the complexity of living organisms.