Are Mental Disorders Brain Diseases, and What Does This Mean? A Clinical-Neuropsychological Perspective

The Tangled Knots of Neuroscientific Experimentation

The experimental method has promoted the popularity of neuroscientific research on the human mind. In this interdisciplinary enterprise, the experimental method, with its roots in natural science and experimental psychology, is often uncritically accepted as the royal road to investigate the human mind not only by neuroscientists, but by many philosophers as well, especially those inclined to some form of naturalism. It is rarely disputed that experiments reveal actual states of nature (here: of mind and/or brain). Experimental results are used to picture the human person or subject as an illusionary construct resulting from neuronal interactions. The present paper sketches some of the limitations of neuroscientific experiments in order to demonstrate that cognitive neuroscience is far from relying on firm methodological grounds. Numerous issues still have to be solved, some of which date back to the early days of modern science. At least, to make experiments work, many theoretical presuppositions have to be accepted and decisions of relevance have to be made in the scientific process. This implies that all scientific endeavor is constituted by persons making free decisions for good reasons, despite all reductionist claims to the contrary. The fact that we as scientists have to distinguish relevant from irrelevant aspects of experimental procedures is also crucial for dealing with the current replicability crisis in the life sciences including neuroscience.

Why mental disorders are brain disorders. And why they are not: ADHD and the challenges of heterogeneity and reification

Scientific attempts to identify biomarkers to reliably diagnose mental disorders have thus far been unsuccessful. This has inspired the Research Domain Criteria (RDoC) approach which decomposes mental disorders into behavioral, emotional, and cognitive domains. This perspective article argues that the search for biomarkers in psychiatry presupposes that the present mental health categories reflect certain (neuro-) biological features, that is, that these categories are reified as biological states or processes. I present two arguments to show that this assumption is very unlikely: First, the heterogeneity (both within and between subjects) of mental disorders is grossly underestimated, which is particularly salient for an example like Attention Deficit/Hyperactivity Disorder (ADHD). Second, even the search for the biological basis of psychologically more basic categories (cognitive and emotional processes) than the symptom descriptions commonly used in mental disorder classifications has thus far been inconclusive. While philosophers have discussed this as the problem of mind-body-reductionism for ages, Turkheimer presented a theoretical framework comparing weak and strong biologism which is more useful for empirical research. This perspective article concludes that mental disorders are brain disorders in the sense of weak, but not strong biologism. This has important implications for psychiatric research: The search for reliable biomarkers for mental disorder categories we know is unlikely to ever be successful. This implies that biology is not the suitable taxonomic basis for psychiatry, but also psychology at large.

Neuroimaging Association Scores: reliability and validity of aggregate measures of brain structural features linked to mental disorders in youth

In genetics, aggregation of many loci with small effect sizes into a single score improved prediction. Nevertheless, studies applying easily replicable weighted scores to neuroimaging data are lacking. Our aim was to assess the reliability and validity of the Neuroimaging Association Score (NAS), which combines information from structural brain features previously linked to mental disorders. Participants were 726 youth (aged 6-14) from two cities in Brazil who underwent MRI and psychopathology assessment at baseline and 387 at 3-year follow-up. Results were replicated in two samples: IMAGEN (n = 1627) and the Healthy Brain Network (n = 843). NAS were derived by summing the product of each standardized brain feature by the effect size of the association of that brain feature with seven psychiatric disorders documented by previous meta-analyses. NAS were calculated for surface area, cortical thickness and subcortical volumes using T1-weighted scans. NAS reliability, temporal stability and psychopathology and cognition prediction were analyzed. NAS for surface area showed high internal consistency and 3-year stability and predicted general psychopathology and cognition with higher replicability than specific symptomatic domains for all samples. They also predicted general psychopathology with higher replicability than single structures alone, accounting for 1-3% of the variance, but without directionality. The NAS for cortical thickness and subcortical volumes showed lower internal consistency and less replicable associations with behavioural phenotypes. These findings indicate the NAS based on surface area might be replicable markers of general psychopathology, but these links are unlikely to be causal or clinically useful yet.

Why Biological Psychiatry Hasn't Delivered Yet - and Why Neurology Knows

It is increasingly recognized that neuroscience has not delivered the revolutionary clinical possibilities for psychiatry that had been promised. Explanations differ, however: some proponents emphasize the divide between biopsychosocial psychiatry and mechanistic neurology. Others rely on further basic experimental neuroscience as only the most elementary level of explanation will allow us to fully understand and treat mental disorders. From a clinical-neuropsychological perspective, I shall argue that both views are mistaken. Diagnosis and treatment of neurological diseases demands a biopsychosocial perspective similar to psychiatry. Acknowledging this might help to bring both disciplines together and improve clinical outcome.

The levels problem in psychopathology

Psychiatric disorders are studied at multiple levels, but there is no agreement on how these levels are related to each other, or how they should be understood in the first place. In this paper, I provide an account of levels and their relationships that is suited for psychopathology, drawing from recent debates in philosophy of science. Instead of metaphysical issues, the focus is on delivering an understanding of levels that is relevant and useful for scientific practice. I also defend a pragmatic approach to the question of reduction, arguing that even in-principle reductionists should embrace pluralism in practice. Finally, I discuss the benefits and challenges in integrating explanations and models of different levels.

Real Neurolaw in the Netherlands: The Role of the Developing Brain in the New Adolescent Criminal Law

Previous publications discussed the conditions under which courts admitted or could admit neurotechnological evidence like brain scans. There were also first attempts to investigate legal decisions neuroscientifically. The present paper analyzes a different way in which neuroscience already influenced the law: The legal justification of the new Dutch adolescent criminal law explicitly mentions findings on brain development to justify a higher maximum age for the application of juvenile criminal law than before. The lawmaker’s reasoning is compared with the neuroscientific studies on which it is based. In particular, three neurodevelopmental publications quoted by the Dutch Council for the Administration of Criminal Justice and Protection of Juveniles to justify that adolescents can be legally less responsible are analyzed in detail. The paper also addresses possibilities under which brain research could improve legal decision-making in the future. One important aspect turns out to be that neuroscience should not only matter on the level of justification, but also provide better instruments on the individual level of application.

Psychiatric manifestations of neurologic diseases: Etiology, phenomenology, and treatment

Understanding the etiology and meaning of behavioral symptomatology in the context of neurologic disease, and choosing the most effective intervention is a vexing task. This introduction summarizes the history of our understanding of the relationship between behavioral symptoms and primary neurologic conditions, and considers the ways in which both psychiatric and neurologic disorders occurring simultaneously may inform both knowledge of etiology and treatment decisions.

[Development through encounter-Kurt Goldstein's contributions to psychotherapy]

The life and works of neurologist and psychiatrist Kurt Goldstein (1878-1965) were almost forgotten for decades but have aroused increasing interest in recent years. Studies on Goldstein generally focus on his groundbreaking contributions to a holistic neurology, neuropsychology and neurorehabilitation; however, his contributions to the development of psychotherapy have received less attention. The present article reviews Goldstein's substantial input to the development of psychotherapy, and especially of humanistic psychotherapies. It is further shown how these contributions are rooted in Goldstein's observations on brain-damaged World War I veterans. From these observations Goldstein derived a holistic view of the organism as a system that embodies and constantly re-establishes an identity, thereby also defining the meaning of anxiety for human existence and drawing conclusions for the therapeutic relationship. It can therefore be argued that brain research impinged on the development of psychotherapy at an early stage, even though its research paradigm differed profoundly from that of present day reductionism.

Subjective Experience, Heterophenomenology, or Neuroimaging? A Perspective on the Meaning and Application of Mental Disorder Terms, in Particular Major Depressive Disorder

Increasing research efforts try to identify biological markers in order to support or eventually replace current practices of diagnosing mental disorders. Inasmuch as these disorders refer to subjective mental states, such efforts amount to their objectification. This gives rise to conceptual as well as empirical challenges: What kind of things are mental disorders? And how to deal with situations where subjective reports, clinical decisions, and brain scans contradict each other? The present paper starts out with a discussion of recent efforts to objectify beauty. Such attempts to quantify and localize psychological constructs in the brain are compared to earlier examples from the history of psychology. The paper then discusses personal and social implications of the objectification of subjective mental states, including mental disorders. The construct of Major Depressive Disorder, one of the most prevalent mental disorders, is then analyzed in more detail. It turns out that this is a very complex construct probably associated with highly heterogeneous actual instances of the disorder. It is then shown that it is unlikely to replace these symptoms’ descriptions with patterns of brain activations, at least in the near future, given these patterns’ empirical lack of specificity. The paper then discusses which of the disorder’s core symptoms are more or less amenable to behavioral or neuroscientific investigation and analyses whether the heterophenomenological method can solve the problem. The conclusion is that the disorder construct is neither entirely subjective, nor completely objectifiable, and that clinical experts do well by continuing to take a pragmatical stance.

How Realistic Are the Scientific Assumptions of the Neuroenhancement Debate? Assessing the Pharmacological Optimism and Neuroenhancement Prevalence Hypotheses

Since two decades, neuroenhancement is a major topic in neuroethics and still receives much attention in the scholarly literature as well as in public media. In contrast to high hopes at the beginning of the “Decade of the Brain” in the United States and Europe that we subsume under the “pharmacological optimism hypothesis,” recent evidence from clinical neuroscience suggests that developing drugs that make healthy people smarter is even more difficult than finding new treatments for patients with mental disorders. However, cognitive enhancing drugs even for patients with impaired intellectual performance have not been successfully developed yet and new drugs that might have a disruptive impact on this field are unlikely to be developed in the near future. Additionally, we discuss theoretical, empirical, and historical evidence to assess whether cognitive enhancement of the healthy is common or even epidemic and if its application will further increase in the near future, as suggested by the “neuroenhancement prevalence hypothesis.” Reports, surveys, and reviews from the 1930s until today indicate that psychopharmacological neuroenhancement is a fact but less common than often stated, particularly in the public media. Non-medical use of psychostimulants for the purpose of cognitive enhancement exists since at least 80 years and it might actually have been more common in the past than today. Therefore, we conclude that the pharmacological optimism hypothesis and neuroenhancement prevalence hypotheses have to be rejected and argue that the neuroenhancement debate should take the available evidence more into account.

[Between psyche and brain : State of the art in psychiatry]

Since its development around 1800 psychiatry has been oscillating between the poles of the sciences and the humanities, being directed towards subjective experience on the one hand and towards the neural substrate on the other hand. Today, this dualism seems to have been overcome by a naturalism, which identifies subjective experience with neural processes, according to Griesinger's frequently quoted statement "mental diseases are brain diseases". The progress achieved by the neurobiological paradigm on the level of a fundamental science is in contrast to the tendency to isolate mental illnesses from the patients' social relationships and to neglect subjectivity and intersubjectivity in their explanation. What should be searched for is therefore an overarching paradigm that is able to establish psychiatry as a relational medicine in an encompassing sense: as a science and practice of biological, psychological and social relationships and their disorders. Within such a paradigm, the brain may be understood and investigated as the central "relational organ" without reductionist constrictions.