Hostname: page-component-586b7cd67f-l7hp2 Total loading time: 0 Render date: 2024-11-27T17:15:21.392Z Has data issue: false hasContentIssue false

Editorial: Considering Transient Instantiators

Published online by Cambridge University Press:  09 November 2020

Jed T. Elison*
Affiliation:
Institute of Child Development, University of Minnesota, Minneapolis, MN, USA Department of Pediatrics, University of Minnesota, Minneapolis, MN, USA
*
Author for Correspondence: Jed T. Elison, 51 East River Parkway, Minneapolis, MN55455; E-mail: [email protected]
Rights & Permissions [Opens in a new window]

Abstract

Type
Special Section Introduction
Copyright
Copyright © Cambridge University Press 2020

“Until we answer that question about heterogeneity, which presupposes answering the specific question of specific etiology, especially how “specificity” is to be construed for a polygenic theory, we do not know whether two labels [or more] are needed, let alone to which patients they should be applied.” Meehl (Reference Meehl, Gottesman and Shields1972) (p. 382).

Among several key themes, the authors of the contributions to this special section of Development and Psychopathology were tasked to address heterogeneity. Core principles of developmental psychopathology such as equifinality and multifinality (Cicchetti & Rogosch, Reference Cicchetti and Rogosch1996) map onto each etiological and phenotypic heterogeneity, respectively. Here, we would like to highlight an additional source of variability that exists between causal pathophysiological instantiators and a phenotypic endpoint, and the conceptual consequences thereof. Temporal heterogeneity, a term borrowed from ecological theory (Dutilleul, Reference Dutilleul2011; Menge & Sutherland, Reference Menge and Sutherland1976) and not unrelated to the concept of chronogeneity (Georgiades, Bishop, & Frazier, Reference Georgiades, Bishop and Frazier2017), considered in the context of neurodevelopmental disorders, captures observed variability in developmental timing as it relates to pathogenesis. Temporal heterogeneity may represent a specific feature of phenotypic heterogeneity. It may also capture evolving patterns of environmental demands that temporally coincide and interact with changes in the developing organism (Lehrman, Reference Lehrman1953). By simply invoking the concept, however, we hope to illustrate a developmental frame, captured by many of the contributions in this special section, but less well appreciated in the broader autism field. Implicit to this framework is an expectation that it is unlikely that a given phenotypic profile will remain stable and persistent, or static over time (Karmiloff-Smith, Reference Karmiloff-Smith1998).

As conceptualized for psychiatric disorders (Insel & Cuthbert, Reference Insel and Cuthbert2015) and autism specifically (Geschwind & State, Reference Geschwind and State2015; Loth, Murphy, & Spooren, Reference Loth, Murphy and Spooren2016), the overarching precision medicine framework explicitly attempts to model etiological and phenotypic heterogeneity in order to deliver the right intervention, at the right dose, to the right person, at the right time (Collins & Varmus, Reference Collins and Varmus2015). Make no mistakes, without an adequate conceptual framework, the right time criterion will remain a thorn in our proverbial side. Following an empirical publication elucidating the phenomenon of temporal heterogeneity as conceptualized herein (Anticevic et al., Reference Anticevic, Corlett, Cole, Savic, Gancsos and Tang2015), albeit with cross-sectional data, Krystal and Anticevic (Reference Krystal and Anticevic2015, p. 738) state “it may be timely to draw attention to one potential source of heterogeneity within and across patients – the dynamic time-dependent neurobiological evolution of schizophrenia across its course of illness.” While the search for biomarkers that could serve as treatment targets for neurodevelopmental disorders is a noble enterprise, the assumption that biomarkers are stable and persistent across time and illness phase requires empirical data to refute or fail to refute said assumption/hypothesis.

Indeed, for a special class of biomarkers, endophenotypes (Gottesman & Gould, Reference Gottesman and Gould2003; Gottesman & Shields, Reference Gottesman and Shields1972), inherent to the definition is that the marker be state independent, or in other words, that it be present whether someone with schizophrenia is in a prodromal state, an actively ill state, or in a state of symptom remission. Quasi-developmentally oriented conceptualizations of the endophenotype also posit that it should be operable prior to any symptom manifestation (Iacono & Malone, Reference Iacono and Malone2011; Lenzenweger, Reference Lenzenweger2013; Skuse, Reference Skuse2001). Additional poignant commentary presaged the observation from Krystal and Anticevic (Reference Krystal and Anticevic2015) referenced above, “[i]deally, to be an appropriate endophenotype, a risk factor should be correlated with disease and/or disease severity but it should be clearly established that this correlation is not a consequence of either medication or degeneration due to disease progression” (Almasy & Blangero, Reference Almasy and Blangero2001, p. 42). “Disease [or rather disorder] progression” is integral to neurodevelopmental disorders – and anchors our conceptualization of temporal heterogeneity. Therefore, unless one clings to the conceptualization of neurodevelopmental or psychiatric phenotypes, and consequently the biomarkers that underlie symptom dimensions or symptom profiles, as stable and persistent, the search for endophenotypes appears less Herculean and more Sisyphean.

If we afford some logical coherence to the concept of temporal heterogeneity, an amendment to the state independence criterion may be warranted. Namely, we propose that an endophenotype must be observed prior to the manifestation of the constellation of features that define a given condition/disorder. Importantly, this marker may or may not persist through the developmental course of the condition/disorder. If it does persist, it may be subsequently obfuscated by disease/disorder progression. Indeed, the likelihood of what Meehl (Reference Meehl, Gottesman and Shields1972) referred to as a potentiator and what we refer to as an instantiator not being obscured by disease/disorder progression is slim. Therefore, the search for transient instantiators that fulfill the expanded list of endophenotype criteria sans the traditional state-independence criterion may yield promising avenues for exploration. This work will not be easy. However, work in this special section showcases the type of developmental thinking that will push us in the right direction.

Acknowledgments

The funders had no role in the writing of this report. JTE expresses his deep appreciation to Dante Cicchetti for his support and mentorship. The ideas herein germinated and were nourished by conversations with and the mentorship of Joe Piven and Irv Gottesman.

Funding Statement

JTE was supported by NIMH R01 MH104324.

Conflicts of Interest

None

References

Almasy, L., & Blangero, J. (2001). Endophenotypes as quantitative risk factors for psychiatric disease: Rationale and study design. American Journal of Medical Genetics (Neuropsychiatric Genetics), 105, 4244.3.0.CO;2-9>CrossRefGoogle ScholarPubMed
Anticevic, A., Corlett, P. R., Cole, M. W., Savic, A., Gancsos, M., Tang, Y., et al. (2015). N-methyl-D-aspartate receptor antagonist effects on prefrontal cortical connectivity better model early than chronic schizophrenia. Biological Psychiatry, 77, 569580.CrossRefGoogle ScholarPubMed
Cicchetti, D., & Rogosch, F. (1996). Editorial: Equifinality and multifinality in developmental psychopathology. Development and Psychopathology, 8, 597600.CrossRefGoogle Scholar
Collins, F. S., & Varmus, H. (2015). A new initiative on precision medicine. New England Journal of Medicine, 372, 793795.CrossRefGoogle ScholarPubMed
Dutilleul, P. R. L. (2011). Spatio-temporal heterogeneity: Concepts and analyses. New York, NY: Cambridge University Press.Google Scholar
Georgiades, S., Bishop, S. L., & Frazier, T. (2017). Editorial perspective: Longitudinal research in autism – introducing the concept of ‘chronogeneity’. Journal of Child Psychology and Psychiatry, 58, 634636.CrossRefGoogle Scholar
Geschwind, D. H., & State, M. W. (2015). Gene hunting in autism spectrum disorder: On the path to precision medicine. Lancet Neurology, 14, 11091120.CrossRefGoogle ScholarPubMed
Gottesman, I. I., & Gould, T. D. (2003). The endophenotype concept in psychiatry: Etymology and strategic intentions. American Journal of Psychiatry, 160, 636645.CrossRefGoogle ScholarPubMed
Gottesman, I. I., & Shields, J. (1972). Schizophrenia and genetics: A twin study vantage point. New York: Academic Press.Google Scholar
Iacono, W. G., & Malone, S. M. (2011). Developmental endophenotypes: Indexing genetic risk for substance abuse with the P300 brain event-related potential. Child Development Perspectives, 5, 239247.CrossRefGoogle ScholarPubMed
Insel, T. R., & Cuthbert, B. N. (2015). Brain disorders? Precisely. Science, 348, 499500.CrossRefGoogle ScholarPubMed
Karmiloff-Smith, A. (1998). Development itself is the key to understanding developmental disorders. Trends in Cognitive Sciences, 2, 389398.CrossRefGoogle ScholarPubMed
Krystal, J. H., & Anticevic, A. (2015). Commentary: Toward illness phase-specific pharmacology for schizophrenia. Biological Psychiatry, 78, 738740.CrossRefGoogle Scholar
Lehrman, D. S. (1953). A critique of Konrad Lorenz's theory of instinctive behavior. Quarterly Review of Biology, 28, 337363.CrossRefGoogle ScholarPubMed
Lenzenweger, M. F. (2013). Thinking clearly about the endophenotype-intermediate phenotype-biomarker distinctions in developmental psychopathology research. Development & Psychopathology, 25, 13471357.CrossRefGoogle ScholarPubMed
Loth, E., Murphy, D. G., & Spooren, W. (2016). Defining precision medicine approaches to autism spectrum disorders: Concepts and challenges. Frontiers of Psychiatry, 7, 188.CrossRefGoogle ScholarPubMed
Meehl, P. E. (1972). A critical afterward. In Gottesman, I. I. & Shields, J. (Eds.), Schizophrenia and genetics: A twin study vantage point (pp. 131189). New York: Academic Press.Google Scholar
Menge, B. A., & Sutherland, J. P. (1976). Species diversity gradients: Synthesis of the roles of predation, competition, and temporal heterogeneity. The American Naturalist, 110, 351369.CrossRefGoogle Scholar
Skuse, D. H. (2001). Endophenotypes and child psychiatry. British Journal of Psychiatry, 178, 395396.CrossRefGoogle ScholarPubMed