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To the Editor: Jason Schiffman, M.A., et al. (1) concluded that "minor physical anomalies may provide important clues to understanding schizophrenia spectrum disorders from a neurodevelopmental perspective" (p. 238). Minor physical anomalies certainly help clarify neurodevelopmental influences in the etiology of schizophrenia, but they may well raise more questions than they answer about the schizophrenia spectrum.
It is known that the prevalence of minor physical anomalies is higher than average in schizophrenia itself (2), and Dr. Schiffman et al. have now demonstrated higher scores for minor physical anomalies in subjects with paranoid and schizotypal personality disorders (1). There is also evidence that minor physical anomalies are greater in people without frank psychotic illness but who experience quasi-psychotic phenomena, such as quasi-delusional beliefs and psychosis proneness (3). Of interest, however, psychosis proneness is associated with smaller skull bases and longer, lower facial heights—features opposite those found in schizophrenia (3).
Furthermore, while high-risk genetic inheritance may (4) or may not (5) correlate with higher levels of minor physical anomalies in high-risk persons who develop schizophrenia, there is no correlation between high-risk genetic inheritance and minor physical anomalies in high-risk persons overall (6, 7). Even when unaffected siblings of persons with schizophrenia are found to have significant minor physical anomalies, these anomalies are quite different from those found in subjects with schizophrenia (8).
Combining these findings, we can conclude that minor physical anomalies in people with schizophrenia 1) are more numerous than those of comparison subjects, 2) are more numerous than, and are different from, those in unaffected people with high-risk genetic inheritance (e.g., offspring, siblings), and 3) are different from those in people with certain quasi-psychotic phenomena.
Thus, while a variety of psychotic and quasi-psychotic conditions may indeed belong on a clinical schizophrenia spectrum, they may well have arrived there by significantly different routes.
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