Research Group 'Psychiatric Genetics', Head: Prof. Dr. Hans H. Stassen

Department of Psychiatry, Psychotherapy and Psychosomatics

Psychiatric Hospital, University of Zurich


Nongenetic Pathologic Developments of Brain-Wave Patterns

Within-Pair EEG Concordance in Healthy Twins

The within-pair EEG concordance of monozygotic (mz) twins is found to be typically as high as r = 0.81 across channels and frequency bands, thus being comparable to that between repeated assessments on the same individual with r = 0.83. Yet our previous investigation into mz twins discordant and concordant for schizophrenia yielded a significantly reduced within-pair EEG concordance for both, the pairs discordant for schizophrenia and the pairs concordant for schizophrenia.

Twins with Schizophrenia

For the within-pair correlation of the global EEG parameter "total power 0-32 Hz", for example, we found a value of r = 0.772 for the healthy twins which is typical of normal mz twins, a reduced value of r = 0.513 for the twins discordant for schizophrenia, and an extremely low correlation of r = 0.210 for the twins concordant for schizophrenia. This marked reduction of within-pair concordance was with 0.488/0.189 [2-5 Hz], 0.484/0.388 [5-8 Hz], 0.642/0.507 [8-12 Hz] and 0.147/0.544 [12-16 Hz] equally true for all power-related EEG parameters in the pairs concordant for schizophrenia.

Affected versus Unaffected Co-Twins

The pairs discordant for schizophrenia displayed a reduction of within-pair concordance for the EEG parameters "centroid" and "symmetry" which measure the power-frequency distribution of frequency bands: 0.258/0.123 [2-5 Hz], 0.294/0.317 [5-8 Hz] and 0.411/0.560 [8-12 Hz]. ANOVAs supported the above results. Specifically, the total EEG power [0-32 Hz] was virtually identical in the healthy co-twins (p > 0.8402), but different between affected and unaffected subjects (p < 0.0001). The severity of illness, as derived from EEG-differences between affected and unaffected subjects, was closely related to the severity of illness as provided by psychopathology syndrome scores.

EEG Anomalies

Consequently, EEG anomalies associated with schizophrenia and manifested differently in the mz co-twins concordant for schizophrenia are likely the effect of nongenetic, pathologic processes that evolved independently in the co-twins’ genetically identical brains once the illness began to progress.


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, Lykken DT, Bomben G: The within-pair similarity of twins reared apart. Eur Arch Psychiatr Neurol Sci 1988; 237: 244-252
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, Propping P: Zwillingsuntersuchungen zur Genetik des normalen Elektroenzephalogramms. In: P. Baumann (ed): Biologische Psychiatrie der Gegenwart, Wien: Springer 1993, 139-144
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
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
Stassen HH, Bomben G, Hell D: Familial brain wave patterns: study of a 12 sib family. Psychiat Genetics 1998; 8: 141-153
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
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
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
Stassen HH: EEG and evoked potentials. In: D. Cooper (ed) Nature Encyclopedia of the Human Genome. Nature Publishing Group, London 2003; 3: 266-269
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
Buckelmüller J, Landolt HP, Stassen HH, Achermann P: Trait-like individual differences in the human sleep EEG. Neuroscience 2006; 138: 351-356

Myriel is a longterm schizophrenic patient whose powerful language, as expressed through her prose and poems, enthrall and fascinate the reader instantaneously. A similar fascination emanates from her paintings and drawings. Thus, her individual suffering, reflected through the power of artistic expression, becomes a depiction of the schizophrenic disorders of the self in general.
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