Another Round of Addiction As A Brain Disease

 

A new open access article looking at the issue of addiction as a brain disease was recently published by Neuropsychopharmacology.  The authors point out that since this original claim as made 20 years ago (7) and subsequently reinforced (8) there have been a flurry of critical articles. On this blog I have examined several of these articles in the past. They parallel typical arguments that are used against psychiatric diagnoses, particularly the concept of psychiatric disorders as diseases.  Interestingly, in this paper that entire issue was summarily addressed:

“Few, if any healthcare professionals continue to maintain that schizophrenia, rather than being a disease, is a normal response to societal conditions. Why, then, do people continue to question if addiction is a disease, but not whether schizophrenia, major depressive disorder or posttraumatic stress disorder are diseases?”  (p. 3)

Any casual observer of the constant arguments on this issue will note a constant flux of how psychiatric disorders are described.  Disorders, conditions, and constructs come to mind.  I always like to point out that actual surveys of both the general public and health care professionals finds that both groups typically classify severe mental illnesses and substance use disorders as diseases, but to varying degrees.  The best surveys of this problem have been done in Finland (4,5) with large sample of doctors, nurses, psychiatrists, laypersons, and politicians included.  In two separate studies the authors asked respondents to consider 60 general conditions and 20 psychiatric conditions.  Respondents were asked to rank the disorders according to which were more similar to disease conditions and different cut offs were used for both samples. In the larger survey of 60 medical and psychiatric conditions – schizophrenia and autism met the survey requirements for disease.  In the second survey, 75% of the respondents considered schizophrenia and autism as diseases and 50% considered Depression, Anorexia, Panic disorder, Generalized Anxiety Disorder, Bulimia, Attention deficit hyperactivity disorder, and Personality disorder to be diseases.  There was more disagreement on Alcoholism and Drug Addiction but 64% of physicians and 74% of psychiatrists considered alcoholism to be a disease.  On the issue of drug addiction 50% of physicians and 65% of psychiatrists considered that condition to be a disease. The authors generally discuss the implications of these opinions from a practical and public policy perspective rather than a medical or philosophical one. The common arguments that persist is that disease status confers social legitimacy on a disorder leading to more treatment resources and hopefully decreasing stigma.  In the case of addictions there are longstanding moral defect or choice theories that essentially equate addiction to willful misconduct. Since large corporations have taken over the healthcare systems in the United States many of these biases are less visible since proprietary rules determine who gets treatment resources and how they are treated. A recent court ruling details how these rules are seriously flawed (6).  An important perspective from the discussion and that is personal experience with the illness by the patient, family members, friends, and employers– a subject I will elaborate on further.

The previous posts on this blog addressed a New England Journal of Medicine article suggesting that addiction was a problem in learning rather than a disease in two separate posts.  Before that I addressed a 2015 article that listed 10 reasons why addictions were not a disease. Responding to these articles highlighted their rhetorical aspect.  Many of the arguments against a disease model of addiction have three basic flaws.  First, they consider the concept of disease to be clearly defined and it is not. Second, they use their more precise definitions for comparison and as a way to prove addiction is not a disease.  And third, they suggest that psychosocial variables are relevant only if the condition in question is not a true disease.  They suggest that real diseases are self-contained and self-perpetuating and that interpersonal relationships and environmental factors cannot modify diseases.  By extension only a medication or a surgical intervention can modify or cure a real disease.  There are many examples of diseases that illustrate why that premise is not true.  In my practice over the past 30 years the most common examples have been diabetes mellitus Type 2, hypercholesterolemia, and hypertension. I have seen many people with extreme cholesterol elevations who were “cured” by a simple dietary change and starting to exercise.  My two previous articles discuss these lines of argumentation.

Another disease feature of substance use disorders is that they can occur in discrete epidemics.  Although epidemics are typically thought of as being associated with infectious diseases, the CDC description is careful to point out that they can also occur as a result of non-infectious diseases like obesity and diabetes mellitus. They also describe 5 conditions that lead to epidemics including an increase in exposure in terms of total amount or increased virulence, introduction of a novel agent, enhanced transmission, a change in host response, or increased host exposure that can occur by new portals of entry.  All 5 of these factors are relevant in drug epidemics.  Substance use disorder epidemics have these features as evidenced by the 20-year opioid epidemic that started with excessive availability of prescriptions opioids and transitioned to more potent illicit opioids. The widespread availability of these compounds come from illicit importation and supply chain proliferation often by opioid users selling these compounds in order to assure that they have an adequate supply.  Over the past 25 years there have been a clear pattern of increased geographic availability of multiple drug classes – leading to increased morbidity and mortality from substance use disorders in these areas.  

Does the current paper add anything to the argument for addiction as a brain disease?  The authors review the history of the more public airing of the concept – an original article by Leshner (7) asserting “addiction is a brain disease” and a follow up article by McClellan (8). The fact that both of these declarations are only about 20 years old should not be lost on anyone. The authors get derailed from the basic concept of disease in the very next paragraph by suggesting “To promote patient access to treatments, scientists need to argue that there is a biological basis beneath challenging behaviors of individuals suffering from addiction.”  The social utility of a diagnosis is separate from its medical and scientific utility. All three are conflated at times (even to the point of suggesting that laypersons should have input into what is a diagnosis), but in my opinion without medical and scientific utility – there is not social utility.

They review the definition of disease – starting with Jellinek’s “The Disease Concept of Alcoholism”.  Jellinek made the argument that diseases were not self-contained “entities” but it is more of an agreed upon label “to describe a cluster of substantial deteriorating changes in the structure or function of the human body and the accompanying deterioration in biopsychosocial functioning”.  That definition is very close to the one I came up with reviewing the work of philosophers Munson and Resnick who defined disease as a “failure of normal functioning”. The main difference is that these two philosophers predicated the definition on the premise that biological systems were programmed processes and those processes failing is what causes the disease.  Adaptive reward based learning can certainly be considered a programmed process in brain biology.  

They take a close look at the idea that any definition of addiction should account for spontaneous remission and non-relapsing states. One of the typical arguments against addiction as a disease is that a significant number of heavy drinkers (and probably cannabis smokers) stop after they graduate from college.  In many ways, excessive alcohol and drug use in college is considered a rite of passage by many Americans.  That rite of passage has a considerable mortality and morbidity on its own that is usually not considered by the addiction as disease critics.  The vast majority of these people are not the people seen by addiction specialists later in life. The people seen in their 40s or 50s will typically give a history of knowing that their pattern of drinking was problematic.  As an example: “I knew from the very first time that I drank a lot more and I drank faster than anyone else. I drank more in college and I did not stop after I graduated”.  And they elaborate on the consequences of excessive alcohol use at every life stage.  Binge use or even fairly continuous use of drugs or alcohol in college is not the same as an addiction.  

The authors point out that some of the epidemiological data used to justify the remission argument is dependent on methodology and population.  For example, a population recruited from a residential treatment facility and interviewed with a standardized interview will yield much different results than a community sample. The diagnosis of addiction (or severe alcohol use disorder) will be stable in the former case but not the latter.  They reference NESARC (National Epidemiological Survey on Alcohol and Related Conditions) as the community sample and using that methodology the baseline lifetime prevalence of non-remitting alcohol dependence was 10% (p. 9).  They also point out that opioid use disorder when observed for 10-30 years has a stable abstinence rate of < 30%.  The fact that some people stop using excessive amounts of drugs or alcohol is not an argument that there is not a large population of people who clearly have a chronic relapsing course and incur significant mortality and morbidity along the way.

The authors proceed to the genetic argument and point out that family and adoption studies point to a heritability of ~50% for addictive disorders. They highlight typical misunderstandings of genetics, specifically the concept of polygenic risk and that fact that some polygenic disorders lead to pathological states – addiction being one of them.  An additional argument is that although the first 20 years of human genome study have been very productive for Mendelian disorders, it has been far less productive for more complex disorders (11). Understanding the human genome is far from complete at this point and some research groups are just beginning to understand the relationships between genetics, addiction, and medication effects (12, 13, 14).

The lesion argument is the next disease straw man to fall. It should be obvious to anyone that diseases do not necessarily produce a discrete lesion either on imaging studies or autopsy.  An yet it remains a favorite to anyone who claims that addictions or psychiatric disorders are not diseases.  They review how imaging is currently used clinically.  This is a reality that most of the critics seem to miss.  If I see brain imaging consistent with small vessel ischemic disease – that alone is insufficient to make the diagnosis. It also requires an adequate history and examination of the patient. The critics apparently have not see radiology reports that point out “clinical correlation is necessary”.  The authors briefly review the functional imaging of alcohol and stimulant use disorders that point to problems with frontal-striatal circuitry, structural changes with alcohol, and demonstrable and expected changes in dopamine signaling. Brain imaging in addiction at this point (apart from the necessary clinical imaging) is useful from a heuristic standpoint – looking for relevant mechanism and treatments, but there is no imaging of addictive disorders per se. 

A popular viewpoint these days is that there is not enough of an investment in psychosocial factors in funded research. Many of those critics make the argument that the trade off should be reduced funding for biological research and those funds should be diverted to psychosocial research. The authors here acknowledge the importance of social factors, their incorporation in more complex research designs, and the fact that a view of addiction as a brain disease in no way negates the importance of other environmental factors. 

The authors address the issue of reductionism.  They use the term determinism instead. Over the past two decades molecular biologists have moved firmly away for the idea that all complex biological systems can be reduced to the basic laws of chemistry and physics. The does not mean that with the appropriate tools biological complexity can not be understood and explained.  Many physicists see the brain as deterministic.  In other words because the brain is made up of particles and those particles must follow the laws of physics, the future (or past state) of any brain can be determined by the right differential equation. Deterministic states can be chaotic and in that situation they are not predictable.  If you believe the brain is deterministic based on physical laws – it follows that there is no free will and that free will is an illusion.  The real limiting factors with describing the brain as deterministic include the following problems:

1.  There are known stochastic factors that introduce random events – some of which are relevant for the addiction.

2.  Complexity – as noted above.  There is so much structure and so many particles that must be considered in these complex systems that there is a clear measurement problem and the most difficult problems are solved by computer modeling approximations rather than mathematically.  I have not seen it discussed but whenever I consider the complexity of biological systems, I see them as an almost infinite set of microenvironments - each with their own physical and chemical parameters. If there was an equation to describe all of those microenvironments acting at one - it would be exceedingly complex.

3.  Brain changes occurring during the addiction process (a large number of which are unknown at this time) alter the deterministic nature of the system.  I suppose the response by the physical determinists would be that the new altered system would be determined by the laws of physics and chemistry. That does not alter the fact that it is a new system with different physical and chemical componenets.

The authors contend that the system is indeterministic because of these factors and therefore free will is allowed.  An associated physics and philosophical question is whether it is really deterministic but unpredictable and why.  Overall, these philosophical arguments do not really seem to add much to the debate.  The critical piece is whether either deterministic or reductionist is used in a pejorative manner.  That use is typically coupled with arguments that other social or psychological theories is what is really happening.  Scientists and physicians are generally interested in knowing all of the details and mechanisms of action. The is the real driver of knowing what is happening at the molecular level.  This paper does a good job of explaining why people who use that approach do not exclude everything else that is going on in the environment.

They end on the issue of compulsivity (or more accurately uncontrolled use) in addiction. It is not the case that this does not happen, but the degree at which it happens.  In the people who I work with practically all of the negative outcomes are associated with uncontrolled use/compulsivity.   That does not mean that people with addictions are automatons. The major treatment modality anywhere is some form of group therapy.  Those groups would not exist if there was an assumptions that people with substance use disorders could not choose to change their thought patterns and behavior.  They continue to have some flexibility, but the probabilities during an active addiction is that the substance use will continue despite negative and in many cases life threatening outcomes. Intact decision making in other areas or even in the focal area of continued substance use with episodes of abstinence does not mean that normal decision making occurs in all areas of life.

In their conclusion, the authors suggest that progress can occur from integrating a number of scientific perspectives including those outside the field of neuroscience.  They advocate for consilience and input from a plurality of disciplines. They also suggest that no single discipline has exclusive ownership of the field.

As a clinician who is used to constant criticism of psychiatry from people who don’t know anything about it – I have a different position.   First, we need to acknowledge the severity of addictions specifically that they kill and disable large numbers of people.  Family members trying to help an afflicted persons know that as well as the difficulty in trying to help them stop.  Second, in rankings of disability compared with other disease states – addictions are consistently in the top 10.  When combined with psychiatric diseases they are ranked second.  There are few other diseases as disabling or lethal.  Third, there have been treatments that are based on the underlying biological factors that are thought to be relevant to addiction that have worked.  Four, it is very clear that individuals with addictions are no longer functioning normally – defined as their normal baseline.  That can start at any point in the life cycle – and at some point most people are aware that they have a severe problem and cannot stop.

All of those factors point to a disease state and it is good to see a paper supporting that opinion.   But even beyond this opinion, consider the people you have known with addictions and make up your own mind based on that experience.  Carefully consider how you interact with people if you consider addiction to be a disease or intentional decision-making.

 

 George Dawson, MD

 

References:

1:  Heilig M, MacKillop J, Martinez D, Rehm J, Leggio L, Vanderschuren LJMJ. Addiction as a brain disease revised: why it still matters, and the need for consilience. Neuropsychopharmacology. 2021 Feb 22. doi: 10.1038/s41386-020-00950-y. Epub ahead of print. PMID: 33619327.

2:  Heilig M, Augier E, Pfarr S, Sommer WH. Developing neuroscience-based treatments for alcohol addiction: A matter of choice? Transl Psychiatry. 2019 Oct 8;9(1):255. doi: 10.1038/s41398-019-0591-6. PMID: 31594920; PMCID: PMC6783461.

3:  Venniro M, Banks ML, Heilig M, Epstein DH, Shaham Y. Improving translation of animal models of addiction and relapse by reverse translation. Nat Rev Neurosci. 2020 Nov;21(11):625-643. doi: 10.1038/s41583-020-0378-z. Epub 2020 Oct 6. PMID: 33024318.

4:  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 Dec 2;2(6):e001632. doi: 10.1136/bmjopen-2012-001632. PMID: 23204142; PMCID: PMC3533011.

5:  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.

6:  Wit v. United Behavioral Health.  Full text of ruling.

7:  Leshner AI. Addiction is a brain disease, and it matters. Science. 1997 Oct 3;278(5335):45-7. doi: 10.1126/science.278.5335.45. PMID: 9311924.

8:  McLellan AT, Lewis DC, O'Brien CP, Kleber HD. Drug dependence, a chronic medical illness: implications for treatment, insurance, and outcomes evaluation. JAMA. 2000 Oct 4;284(13):1689-95. doi: 10.1001/jama.284.13.1689. PMID: 11015800.

9:  Koob GF, Volkow ND. Neurobiology of addiction: a neurocircuitry analysis. Lancet Psychiatry. 2016 Aug;3(8):760-773. doi: 10.1016/S2215-0366(16)00104-8. PMID: 27475769; PMCID: PMC6135092.

10:  Volkow ND, Morales M. The Brain on Drugs: From Reward to Addiction. Cell. 2015 Aug 13;162(4):712-25. doi: 10.1016/j.cell.2015.07.046. PMID: 26276628.

11:  Koob GF, Powell P, White A. Addiction as a Coping Response: Hyperkatifeia, Deaths of Despair, and COVID-19. Am J Psychiatry. 2020 Nov 1;177(11):1031-1037. doi: 10.1176/appi.ajp.2020.20091375. PMID: 33135468.

12.  Miga KH. Breaking through the unknowns of the human reference genome. Nature. 2021 Feb;590(7845):217-218. doi: 10.1038/d41586-021-00293-8. PMID: 33568817.

13:  Ho MF, Zhang C, Zhang L, Wei L, Zhou Y, Moon I, Geske JR, Choi DS, Biernacka J, Frye M, Wen Z, Karpyak VM, Li H, Weinshilboum R. TSPAN5 influences serotonin and kynurenine: pharmacogenomic mechanisms related to alcohol use disorder and acamprosate treatment response. Mol Psychiatry. 2020 Aug 4:10.1038/s41380-020-0855-9. doi: 10.1038/s41380-020-0855-9. Epub ahead of print. PMID: 32753686; PMCID: PMC7858703.

14:   Nguyen TTL, Liu D, Ho MF, Athreya AP, Weinshilboum R. Selective Serotonin Reuptake Inhibitor Pharmaco-Omics: Mechanisms and Prediction. Front Pharmacol. 2021 Jan 11;11:614048. doi: 10.3389/fphar.2020.614048. PMID: 33510640; PMCID: PMC7836019.