EEG differences in monozygotic twins discordant and concordant for schizophrenia

In an electroencephalographic (EEG) study of 27 pairs of monozygotic (MZ) t wins discordant for schizophrenia, 13 pairs of MZ twins concordant for schi zophrenia, 40 pairs of healthy MZ twins, and 91 healthy, unrelated subjects with repeated assessments, we investigated (a) the trait quality of brainw ave patterns with respect to interindividual differences, intraindividual s tability over time, and within-pair MZ concordance; (b) the EEG characteris tics that enable discrimination between affected and unaffected individuals ; and (c) the EEG characteristics that reflect the severity of illness. In comparison with healthy control subjects, the MZ twins who were discordant and concordant for schizophrenia exhibited a much lower within-pair EEG con cordance, so that EEG abnormalities associated with schizophrenia and manif ested differently in the co-twins concordant for schizophrenia seemed to re flect nongenetic, pathological developments of genetically identical brains .