Online research in philosophy

This paper argues for psychological realism in the conception of psychiatric disorders. We review the following contemporary ways of understanding the future of psychiatry: (1) psychiatric classification cannot be successfully reduced to neurobiology, and thus psychiatric disorders should not be conceived of as biological kinds; (2) psychiatric classification can be successfully reduced to neurobiology, and thus psychiatric disorders should be conceived of as biological kinds. Position (1) can lead either to instrumentalism or to eliminativism about psychiatry, depending on whether psychiatric classification is regarded as useful. Position (2), which is inspired by the growing interest in neuroscience within scientific psychiatry, leads to biological realism or essentialism. In this paper we endorse a different realist position, which we label psychological realism. Psychiatric disorders are identified and addressed on the basis of their psychological manifestations which are often described as violations of epistemic, moral or social norms. A couple of examples are proposed by reference to the pathological aspects of delusions, and the factors contributing to their formation.

I distinguish three evolutionary explanations of mental illness: first, breakdowns in evolved computational systems; second, evolved systems performing their evolutionary function in a novel environment; third, evolved personality structures. I concentrate on the second and third explanations, as these are distinctive of an evolutionary psychopathology, with progressively less credulity in the light of the empirical evidence. General morals are drawn for evolutionary psychiatry.

Evolutionary psychiatrists invariably consider schizophrenia to be a paradox: how come natural selection has not yet eliminated the infamous ‘genes for schizophrenia’ if the disorder simply crushes the reproductive success of its carriers, if it has been around for thousands of years already, and if it has a uniform prevalence throughout the world? Usually, the answer is that the schizophrenic genotype is subject to some kind of balancing selection: the benefits it confers would then outbalance the obvious damage it does. In this paper, however, I will show that the assumptions underlying such evolutionary accounts of schizophrenia are at least implausible, and sometimes even erroneous. First of all, I will examine some factual assumptions, in particular about schizophrenia’s impact on reproductive success, its genetics, its history, and its epidemiology. Secondly, I will take a critical look at a major philosophical assumption in evolutionary psychiatric explanations of schizophrenia. Indeed, evolutionary psychiatrists take it for granted that schizophrenia is a natural kind, i.e. a bounded and objectively real entity with discrete biological causes. My refutation of this natural kind view suggests that schizophrenia is in fact a reified umbrella concept, covering a heterogeneous group of disorders. Therefore, schizophrenia, as we now know it, simply doesn’t have an evolutionary history.

The target article shows that the application of the evolutionary theory to psychopathology should not necessarily consist in finding hidden adaptive benefits for each psychiatric syndrome. However, in rejecting lax adaptationism, Darwinian psychiatrists should not forget that the search for adaptive behavioral polymorphisms can be a powerful antidote against the normative attitude of mainstream psychiatry and its growing tendency to medicalize human diversity. (Published Online November 9 2006).

The only commonality between the various psychiatric disorders is that they reflect contemporary problematic behaviors. Some psychiatric disorders have a substantial genetic component, whereas others are essentially shaped by prevailing environmental factors. Because psychiatric ailments are so heterogeneous, any universal explanation of mental illness is not likely to have any clinical or theoretical utility. (Published Online November 9 2006).

This response (a) integrates non-equilibrium evolutionary genetic models, such as coevolutionary arms-races and recent selective sweeps, into a framework for understanding common, harmful, heritable mental disorders; (b) discusses the forms of ancestral neutrality or balancing selection that may explain some portion of mental disorder risk; and (c) emphasizes that normally functioning psychological adaptations work against a backdrop of mutational and environmental noise. (Published Online November 9 2006).

This paper will consider the right not to know in the context of psychiatric disorders. It will outline the arguments for and against acquiring knowledge about the results of genetic testing for conditions such as breast cancer and Huntington’s disease, and examine whether similar considerations apply to disclosing to clients the results of genetic testing for psychiatric disorders such as depression and Alzheimer’s disease. The right not to know will also be examined in the context of the diagnosis of psychiatric disorders that are associated with stigma or for which there is no effective treatment.

Maladapting Minds discusses a number of reasons why philosophers of psychiatry should take an interest in evolutionary explanations of mental disorders and, more generally, in evolutionary thinking. First of all, there is the nascent field of evolutionary psychiatry. Unlike other psychiatrists, evolutionary psychiatrists engage with ultimate, rather than proximate, questions about mental illnesses. Being a young and youthful new discipline, evolutionary psychiatry allows for a nice case study in the philosophy of science. Secondly, philosophers of psychiatry have engaged with evolutionary theory because evolutionary considerations are often said to play a role in defining the concept of mental disorder. The basic question here is: Can the concept of mental disorder be given an objective definition, or is it rather a normative concept? Thirdly and finally, evolutionary thinking in psychiatry has often been a source of inspiration for a philosophical view on human nature. Thus evolutionary psychiatrists have suggested, for example, that man's vulnerability to mental disorders may well be one of the defining features of our species.

Written by leading authors in philosophy, psychiatry, biology and psychology, this volume illustrates that many debates in contemporary philosophy of psychiatry are profoundly influenced by evolutionary approaches to mental disorders. Conversely, it also reveals how philosophers can help contribute to the burgeoning field of evolutionary psychiatry. It is important reading for a wide range of readers interested in mental health care and philosophy.

An evolutionary theory of schizophrenia needs to address all symptoms associated with the condition. Burns' framework could be extended in a way embracing behavioural signs such as catatonia. Burns' theory is, however, not specific to schizophrenia. Since no one single symptom exists that is pathognomonic for “schizophrenia,” an evolutionary proposal of psychiatric disorders raises the question whether our anachronistic psychiatric nosology warrants revision.

Given that natural selection is so powerful at optimizing complex adaptations, why does it seem unable to eliminate genes (susceptibility alleles) that predispose to common, harmful, heritable mental disorders, such as schizophrenia or bipolar disorder? We assess three leading explanations for this apparent paradox from evolutionary genetic theory: (1) ancestral neutrality (susceptibility alleles were not harmful among ancestors), (2) balancing selection (susceptibility alleles sometimes increased fitness), and (3) polygenic mutation-selection balance (mental disorders reflect the inevitable mutational load on the thousands of genes underlying human behavior). The first two explanations are commonly assumed in psychiatric genetics and Darwinian psychiatry, while mutation-selection has often been discounted. All three models can explain persistent genetic variance in some traits under some conditions, but the first two have serious problems in explaining human mental disorders. Ancestral neutrality fails to explain low mental disorder frequencies and requires implausibly small selection coefficients against mental disorders given the data on the reproductive costs and impairment of mental disorders. Balancing selection (including spatio-temporal variation in selection, heterozygote advantage, antagonistic pleiotropy, and frequency-dependent selection) tends to favor environmentally contingent adaptations (which would show no heritability) or high-frequency alleles (which psychiatric genetics would have already found). Only polygenic mutation-selection balance seems consistent with the data on mental disorder prevalence rates, fitness costs, the likely rarity of susceptibility alleles, and the increased risks of mental disorders with brain trauma, inbreeding, and paternal age. This evolutionary genetic framework for mental disorders has wide-ranging implications for psychology, psychiatry, behavior genetics, molecular genetics, and evolutionary approaches to studying human behavior. (Published Online November 9 2006) Key Words: adaptation; behavior genetics; Darwinian psychiatry; evolution; evolutionary genetics; evolutionary psychology; mental disorders; mutation-selection balance; psychiatric genetics; quantitative trait loci (QTL).