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Institute for Response-Genetics (e.V.)

Prof. Dr. Hans H. Stassen, Chairman

(Formerly Associated Institute of the University of Zurich)

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MZ Twins Discordant for Schizophrenia

Within-Pair EEG Concordance

In an EEG study of 91 healthy subjects with repeated assessments, 40 pairs of healthy MZ twins, 27 pairs of MZ twins discordant for schizophrenia, and 13 pairs of MZ twins concordant for schizophrenia, we investigated (1) the trait quality of brain-wave patterns with respect to inter-individual differences, intra-individual stability over time, and within-pair MZ concordance, (2) the characteristics of brain-wave patterns that allow one to discriminate reliably between affected and unaffected individuals, and (3) the characteristics of brain-wave patterns that reflect the severity of illness. Most parameters chosen to quantify brain-wave characteristics were found to possess distinct trait-like qualities, as indicated by large inter-individual differences, great stability over time, and high within-pair concordances in healthy MZ twins.

Non-Genetic Pathologic Brain Developments

In comparison to healthy controls, MZ twins discordant and concordant for schizophrenia exhibited a much lower within-pair EEG concordance, although the majority of correlation coefficients differed significantly from zero. Accordingly, abnormalities of brain-wave patterns associated with schizophrenia and differently manifested in MZ co-twins concordant for schizophrenia seem to reflect non-genetic, idiosynchratic pathologic developments of genetically identical brains. These abnormalities allowed us to discriminate reproducibly between affected and unaffected individuals by means of a multivariate discriminant function with an overall accuracy of 80%.

Severity of Illness

The severity of illness, as derived from the brain-wave discriminant function, was closely related to the severity of illness provided by psychopathology scores and overall AXIS V social functioning. In consequence, the non-genetic, highly individual pathologic development of brain-wave patterns in schizophrenia clearly limit the usefulness of these quantities as biological markers for investigations into the genetic predisposition to this illness.

References

Stassen HH, Bachmann S, Bridler R, Cattapan K, Herzig D, Schneeberger A, Seifritz E. Inflammatory Processes linked to Major Depression and Schizophrenic Disorders and the Effects of Polypharmacy in Psychiatry: Evidence from a longitudinal Study of 279 Patients under Therapy. Eur Arch Psychiatry Clin Neurosci. 2021; 271(3): 507-520 [get the article]
Braun S, Bridler R, Müller N, Schwarz MJ, Seifritz E, Weisbrod M, Zgraggen A, Stassen HH: Inflammatory Processes and Schizophrenia: Two Independent Lines of Evidence from a Study of Twins Discordant and Concordant for Schizophrenic Disorders. Eur Arch Psychiatry Clin Neurosci 2017; 267: 377-389 [get the article]
Braun S, Bridler R, Müller N, Schwarz MJ, Seifritz E, Weisbrod M, Zgraggen A, Stassen HH: Inflammatory Processes and Schizophrenia: Two Independent Lines of Evidence From a Study of Twins Discordant and Concordant for Schizophrenic Disorders. Neuropsychopharmacology 2016; 41: S414–S415
Stassen HH, Delfino JP, Kluckner VJ, Lott P, Mohr C: Vulnerabilität und psychische Erkrankung. Swiss Archives of Neurology and Psychiatry 2014; 165(5): 152-157
Stassen HH, Angst J, Hell D, Scharfetter C, Szegedi A: Is there a common resilience mechanism underlying antidepressant drug response? Evidence from 2'848 patients. J Clin Psychiatry 2007; 68(8): 1195-1205
Buckelmüller J, Landolt HP, Stassen HH, Achermann P: Trait-like individual differences in the human sleep EEG. Neuroscience 2006; 138: 351-356
Weisbrod M, Hill H, Sauer H, Niethammer R, Guggenbühl S, Stassen HH: Nongenetic pathologic developments of brain-wave patterns in monozygotic twins discordant and concordant for schizophrenia. Am J Med Genetics B 2004; 125: 1-9
Stassen HH: EEG and evoked potentials. In: D. Cooper (ed) Nature Encyclopedia of the Human Genome. Nature Publishing Group, London 2003; 3: 266-269
Umbricht D, Koller R, Schmid L, Skrabo A, Grübel C, Huber T, Stassen HH: How specific are deficits in mismatch negativity generation to schizophrenia? Biol Psychiatry 2003; 53: 1120-1131
Dünki RM, Schmid GB, Stassen HH: Intraindividual specificity and stability of the human EEG: Linear vs. nonlinear approaches. Meth Inform Med 2000; 39: 78-82
Stassen HH, Coppola R. Torrey EF, Gottesman II, Kuny S, Rickler KC, Hell D: EEG differences in monozygotic twins discordant and concordant for schizophrenia. Psychophysiology 1999; 36,1: 109-117
Stassen HH, Bomben G, Hell D: Familial brain wave patterns: study of a 12 sib family. Psychiat Genetics 1998; 8: 141-153
Dünki RM, Schmid GB, Scheidegger P, Stassen HH, Bomben G, Propping P: Reliable computer-assisted classification of the EEG: EEG variants in index cases and their first-degree relatives. Am J Med Genetics B 1996; 67,1: 1-8
Kaprio J, Buchsbaum M, Gottesman II, Heath A, Körner J, Kringlen E, McGuffin P, Propping P, Rietschel M, Stassen HH: What can twin studies contribute to the understanding of adult psychopathology? In: T.J. Bouchard jr. and P. Propping: Twins as a tool for behavioral genetics. Chichester: John Wiley & Sons, Dahlem Workshop Reports, Life Sciences Research Report 1993; 53: 287-299
Stassen HH, Lykken DT, Propping P: Zwillingsuntersuchungen zur Genetik des normalen Elektroenzephalogramms. In: P. Baumann (ed): Biologische Psychiatrie der Gegenwart, Wien: Springer 1993, 139-144
Stassen HH, Lykken DT, Propping P, Bomben G: Genetic determination of the human EEG (survey of recent results from twins reared together and apart). Human Genetics 1988; 80: 165-176
Stassen HH, Lykken DT, Bomben G: The within-pair similarity of twins reared apart. Eur Arch Psychiatr Neurol Sci 1988; 237: 244-252
Stassen HH, Bomben G, Propping P: Genetic aspects of the EEG: an investigation into the within-pair similarity of monozygotic and dizygotic twins with a new method of analysis. Electroenceph clin Neurophysiol 1987; 66: 489-501
Stassen HH: The similarity approach to EEG analysis. Meth Inform Med 1985; 24: 200-212
Stassen HH: Computerized recognition of persons by EEG spectral patterns. Electroenceph clin Neurophysiol 1980; 49: 190-194

 

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Absolute power 7.5-15 Hz
Distribution of the EEG parameter "absolute power 7.5-15 Hz" in the general population: the figure shows an approximately normal, slightly right-skewed distribution with a mean value of 464.7 and a standard deviation of 157.7 (note that values>600 appear in the right-most bar of the plot). The experimental condition is quiet wakefulness (eyes closed) and the channel is T5-O1.
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