Am J Psychiatry 1992; 149:1355-1361
Copyright © 1992 by American Psychiatric Association
Second-trimester markers of fetal size in schizophrenia: a study of monozygotic twins
HS Bracha, EF Torrey, II Gottesman, LB Bigelow and C Cunniff
Department of Psychiatry and Behavioral Sciences, University of Arkansas for Medical Sciences, Little Rock.
OBJECTIVE: Since the second prenatal trimester is the critical period of
massive neural cell migration to the cortex, and fingertip dermal cells
migrate to form ridges during this same period, the authors sought to
determine whether there are differences in fingertip ridge count in pairs
of monozygotic twins discordant for schizophrenia, possibly indicating that
a prenatal anatomical insult affected the twins differently. METHOD: The
fingertip dermal ridges of 30 pairs of monozygotic twins (23 pairs in which
the twins were discordant for schizophrenia and seven pairs in which both
twins were normal) were counted by two persons trained in anthropometric
research. Intrapair differences in the counts were then measured, and the
differences among the pairs of normal twins were compared with the
differences among the pairs discordant for schizophrenia. RESULTS: The
twins discordant for schizophrenia had significantly greater absolute
intrapair differences in total finger ridge count and significantly greater
percent intrapair differences than the normal twins; i.e., their
fingerprints were significantly less "twin-like." CONCLUSIONS: The study
suggests that various second-trimester prenatal disturbances in the
epigenesis of one twin in a pair discordant for schizophrenia may be
related to the fact that only one of the twins expresses his or her genetic
predisposition toward schizophrenia. This is consistent with a "two-strike"
etiology of schizophrenia: a genetic diathesis plus a second-trimester
environmental stressor.
