Identical Twins Discordant for Schizophrenia

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Abstract
Neurologic findings in 22 identical twin pairs (15 discordant for schizophrenia, three concordant, and four psychologically normal) are reported. Based on two careful examinations, 11 indexes in the discordant pairs, two schizophrenics in the concordant pairs, and two normal twins were judged as probably or definitely neurologically abnormal. Significantly more abnormal signs were found in discordant indexes than in their co-twins, in schizophrenics than in nonschizophrenics, and in lower birth weight than in higher birth weight twins. Although two electroencephalograms on each twin revealed few clear abnormalities and striking intrapair concordance, half of the sample had some minor deviation from normal on at least one EEG. Significant correlations were found between neurologic scores and both Wechsler Adult Intelligence Scale (WAIS) IQ and level of psychopathology on several Inpatient Multidimensional Psychiatric Scale (IMPS) subscales. Interpretations of these data and requirements for future studies are considered.