Overview

2. Overview • Presentation 1 (April 20, 2007) • Evolutionary psychiatry: an introduction • Based on De Block & Adriaens (2004) • Presentation 2 (May 4, 2007) • EP and the schizophrenia paradox: a critique • Based on Adriaens (in press) Evolutionary psychiatry and the schizophrenia paradox: a critique

3. EP and the schizophrenia paradox: a critique 1. Meet the schizophrenia paradox 2. A paradox and its resolutions 3. A paradox and its assumptions 4. What, if anything, is schizophrenia? 5. Some conclusions Evolutionary psychiatry and the schizophrenia paradox: a critique

4. A paradox Resolutions Assumptions Philosophy Conclusion 1. Meet the schizophrenia paradox • A paradox vis-à-vis natural (and sexual?) selection: • ‘If, as appears likely, genetic factors are of some importance in the aetiology of schizophrenia, and if the schizophrenics, due to their reduced fertility, contribute fewer descendants than comparable members of the normal population, why does schizophrenia not become a great rarity, instead of remaining so common?’ (Carter & Watts 1971) • Is the schizophrenia paradox really a paradox? • ‘While hurrying to resolve the paradox, evolutionary psychiatrists have failed to check the truth value of their assumptions, i.e. about schizophrenia’s impact on reproductive success, its genetics, its history and its epidemiology’ (Adriaens, in press) Evolutionary psychiatry and the schizophrenia paradox: a critique

5. A paradox Resolutions Assumptions Philosophy Conclusion Diagnostic criteria for schizophrenia (DSM-IV) A. Characteristic symptoms: Two (or more) of the following, each present for a significant portion of time during a 1-month period (1) delusions (2) hallucinations (3) disorganized speech (e.g. incoherence) (4) grossly disorganized or catatonic behavior (5) negative symptoms, i.e. affective flattening, alogia, or avolition Note: Only one criterion A symptom is required if delusions are bizarre or hallucinations consist of a voice keeping up a running commentary on the person’s behavior or thoughts, or two or more voices conversing with each other B. Social/occupational dysfunction: For a signficant portion of the time since the onset of the disturbance, one or more major areas of functioning such as work, interpersonal relations, or self-care are markedly below the level achieved prior to onset C. Duration: Continuous signs of the disturbance persist for at least 6 months. This 6-month period must include at least 1 month of symptoms that meet criterion A Evolutionary psychiatry and the schizophrenia paradox: a critique

6. The mismatch-model (e.g. Polimeni & Reiss 2002) The trade-off model (see next page) The adaptationist model (none) The polygenic mutation-selection model (K & M 2006) The novelty-model (e.g. Torrey 1980) The cancer-model (none) A paradox Resolutions Assumptions Philosophy Conclusion 2. A paradox and its resolutions Evolutionary psychiatry and the schizophrenia paradox: a critique

7. A paradox Resolutions Assumptions Philosophy Conclusion The trade-off model • The putative ‘genes for schizophrenia’ may also offer unusual advantages • The prototypical example: sickle cell anaemia: • ‘In a sense, schizophrenic genes are like the genes responsible for sickle cell anaemia, which enhance the well-being of carriers by protecting them from malaria while impairing those with greater genetic loading by afflicting them with anaemia’ (Stevens & Price 1996) • What advantages? Evolutionary psychiatry and the schizophrenia paradox: a critique

8. A paradox Resolutions Assumptions Philosophy Conclusion The trade-off model (continued) • Physiological advantages: • Enhanced resistance to surgical and wound shock, pain, infectious diseases, allergies (dermatitis, asthma, pollinosis, urticaria,…), high doses of histamine, etcetera (Huxley et al. 1964; Erlenmeyer-Kimling 1968; Carter & Watts 1971) • Enhanced fertility of female relatives of schizophrenics (Avila et al. 2003) • Psychological advantages: • Enhanced social cognition (Burns 2004) or linguistic (Crow 2000) abilities • Enhanced creativity of (some) schizophrenic patients and/or their relatives (e.g. Karlsson 2001; Nettle 2001; Horrobin 2001) Evolutionary psychiatry and the schizophrenia paradox: a critique

9. = Has been said to be schizophrenic OR to have schizophrenic relatives A paradox Resolutions Assumptions Philosophy Conclusion Meet some mad geniuses (from Post 1994) Nash Watson Newton Evolutionary psychiatry and the schizophrenia paradox: a critique

10. = Has been said to be schizophrenic OR to have schizophrenic relatives A paradox Resolutions Assumptions Philosophy Conclusion Meet some mad geniuses (continued) Artaud (A) Evolutionary psychiatry and the schizophrenia paradox: a critique

11. = Has been said to be schizophrenic OR to have schizophrenic relatives A paradox Resolutions Assumptions Philosophy Conclusion Meet some mad geniuses (continued) Evolutionary psychiatry and the schizophrenia paradox: a critique

12. A paradox Resolutions Assumptions Philosophy Conclusion Some problems • Trade-offs like sickle cell anaemia are rather rare, and they are provisional because they are costly: • ‘Selection would strongly favour genetic events that positions both S and s on the same chromosomal arm, so they can be passed on together without disruption, or mutations that reduce the fitness costs of either homozygote’ (Keller & Miller 2006) • Most scenarios involving physiological advantages have not been replicated (Allen & Sarich 1988), while those involving psychological advantages suffer from either methodological or definitional deficits (Waddell 1998) • Nearly all just-so stories about schizophrenia are based on a number of dubious factual as well as philosophicalassumptions (see next section) Evolutionary psychiatry and the schizophrenia paradox: a critique

13. A paradox Resolutions Assumptions Philosophy Conclusion 3. A paradox and its assumptions • Schizophrenia reduces reproductive success • There are such things as ‘genes for schizophrenia’ • Schizophrenia has been around for tens of thousands of years • Schizophrenia has a uniform prevalence throughout the world • Schizophrenia is a natural kind (see next section) Evolutionary psychiatry and the schizophrenia paradox: a critique

14. A paradox Resolutions Assumptions Philosophy Conclusion 3.1 Schizophrenia and fertility • Are schizophrenics really at a selective disadvantage? Yes, but there is: • intersex variability: fertility of female schizophrenics in Palau was only slightly lower than the average Micronesian female fertility (Sullivan et al. 2007); AND marital fertility of male schizophrenics in Ireland was higher than the marital fertility of female Irish schizophrenics (Lane et al. 1995) • ethnic-geographic variability: male Indian schizophrenics were much more likely to marry than male American schizophrenics (29 versus 4%, respectively) (Bhatia et al. 2003) • Have they always been at a selective disadvantage? Not necessarily: • ‘Schizophrenia may have been a somewhat, or even much, milder illness than we have recognized in the past 150 years’ (Horrobin 2001) • In times past and/or in other cultures, schizophrenics may (have) be(en) shamans or priests (Silverman 1967; Polimeni & Reiss 2002) Evolutionary psychiatry and the schizophrenia paradox: a critique

15. Evolutionary psychiatry and the schizophrenia paradox: a critique

16. A paradox Resolutions Assumptions Philosophy Conclusion 3.2 Schizophrenia and genetics • Question: are there such things as ‘genes for schizophrenia’? 1. Yes, and we’re talking about an orderly and limited number of major impact genes (the trade-off model) • ‘Several major genes must be simultaneously present in the same individual if that person is to be schizophrenic. We don’t know how many “several” is, but three or four would not be an unreasonable guess’ (Horrobin 2001) 2. Yes, but mapping them will be wildly more complicated than psychiatric geneticists have ever thought (K&M’s model) • ‘Mutations contributing to the development of schizophrenia are probably scattered across a myriad of locations in our genome, while their effect size will be very small’ (Adriaens, in press) Evolutionary psychiatry and the schizophrenia paradox: a critique

17. A paradox Resolutions Assumptions Philosophy Conclusion 3.2 Schizophrenia and genetics (continued) • Fact: schizophrenia has a high heritability (~80%) 1. Some optimistic notes: • A single dominant gene, with low penetrance (Böök 1953) • A chromatographic urine analysis (Huxley et al. 1964) • A (predictive) whole-brain MRI scan (Davatzikos et al. 2005) 2. Some pessimistic notes: • ‘Schizophrenia is still a disease whose mechanism is totally unknown’ (Holden 2003) • If the predictions of the trade-off model would be correct, psychiatric genetics would have found the schizophrenia susceptibility genes already (K&M 2006) Evolutionary psychiatry and the schizophrenia paradox: a critique

18. A paradox Resolutions Assumptions Philosophy Conclusion 3.3 The history of schizophrenia • Question: how long has the illness been around? 1. Long enough to be amenable to natural selection, i.e. at least 80 000 years ago (Burns 2004) 2. As it is a disease of civilization, perhaps due to a virus (Torrey 1980), or to the reduced intake of essential fatty acids (Horrobin 2001), it is barely 200 years old 3. As schizophrenia is an umbrella concept, some of the disorders it covers may be quite old. However, schizophrenia itself, as we now know it, was invented by psychiatry (Boyle 1990; Adriaens, in press) • Fact: there are barely any descriptions of schizophrenia (as we now know it) before 1800 (Evans et al. 2003) Evolutionary psychiatry and the schizophrenia paradox: a critique

19. A paradox Resolutions Assumptions Philosophy Conclusion 3.4 The epidemiology of schizophrenia • Question: does schizophrenia have a worldwide uniform prevalence? 1. Yes, and the average prevalence would be between 0.7 and 1.0 per cent: 2. No, prevalence studies have yielded a diversity of results: • High prevalence rates in the North of Sweden, Western Ireland, and the Northwest of Croatia (Torrey 1987; McGrath 2005) • Low prevalence rates among the Amish in the US, among Taiwanese aboriginals, and in Ghana (Ibid.) • Cross-cultural variability could reorientate research on schizophrenia (Sullivan et al. 2007) • ‘In all populations of the world, from the Canadian Arctic to Patagonia, from Lapland to the Cape of Good Hope, from Siberia to the world of the Australian Aborigines, the picture is the same’ (Jablensky et al. 1992; Horrobin 2001) Evolutionary psychiatry and the schizophrenia paradox: a critique

20. A paradox Resolutions Assumptions Philosophy Conclusion A preliminary conclusion • If schizophrenia is due to a myriad of mutations… • If its impact on reproductive fitness is not necessarily dramatic (and perhaps even above average)… • If the disorder is only a few hundred years old… • If its prevalence is highly variable throughout the world… • …then the persistence of schizophrenia need not necessarily be a paradox for evolutionary theory. • But what exactly is schizophrenia, philosophically speaking? Evolutionary psychiatry and the schizophrenia paradox: a critique

21. A paradox Resolutions Assumptions Philosophy Conclusion 4. What, if anything, is schizophrenia? • Question: is schizophrenia a natural kind? • A natural kind is a bounded entity with fixed internal properties, enabling us to identify the entity in question, and to distinguish it (preferably biologically) from other, related entities • The prototypical example of a natural kind: a quark • If schizophrenia (as a diagnostic category) is a natural kind, then • it would be indifferent to changes in psychiatric diagnostics • It would be a bounded category vis-à-vis other disorders and normality • It would be grounded in discrete biological causes (not discussed) Evolutionary psychiatry and the schizophrenia paradox: a critique

22. A paradox Resolutions Assumptions Philosophy Conclusion 4.1 Schizophrenia and psychiatric diagnostics • No: there is a striking coincidence between conceptual alterations in psychiatry on the one hand, and the epidemiology of schizophrenia on the other hand concept of schizophrenia (number of) patients suffering from schizophrenia • Thus schizophrenia is a moving target, an interactive kind (Hacking 1999) Evolutionary psychiatry and the schizophrenia paradox: a critique

23. A paradox Resolutions Assumptions Philosophy Conclusion 4.2 Schizophrenia and mental health • No, it is difficult to distinguish schizophrenia from normality and other mental disorders because • it is impossible to group schizophrenic patients on the basis of some unique and observable set of features (e.g. neurophysiological abnormalities • it is extremely difficult to detect statistically significant differences between the three populations mentioned above (Heinrichs 2001) • In short: schizophrenic patients may have no symptoms in common at all (Fanous & Kendler 2005), while they have lots of ‘symptoms’ in common with other psychiatric patients and healthy individuals (e.g. hallucinations; Bentall 2003) Evolutionary psychiatry and the schizophrenia paradox: a critique

24. A paradox Resolutions Assumptions Philosophy Conclusion An alternative: the heterogeneity hypothesis • Schizophrenia is an umbrella concept, covering, for example: • Some mild organic brain disorders (Bleuler 1911) • A number of infectious diseases (Ibid.) • Cases of Encephalitis lethargica (Boyle 1990) • Wilson’s disease (Keller & Miller 2006) • ‘The heterogeneity hypothesis would explain why, at any level (neuroanatomic, genetic, symptomatologic,…) researchers find it so hard to detect any consistent common denominator in any given group of schizophrenic patients’ (Adriaens, in press) Evolutionary psychiatry and the schizophrenia paradox: a critique

25. A paradox Resolutions Assumptions Philosophy Conclusion 5. Some conclusions • A cautionary tale: what are we trying to explain? • If the four assumptions mentioned above are at least dubious, and if schizophrenia is not a natural kind, then there is perhaps little to be gained by pursuing fancy hypotheses about its evolution • Evolutionary psychiatrists should be in touch with other disciplines, such as, for example, evolutionary genetics, the history of psychiatry, and psychiatic epidemiology Evolutionary psychiatry and the schizophrenia paradox: a critique

26. Merci! Evolutionary psychiatry and the schizophrenia paradox: a critique