Is schizophrenia a genetic illness? One approach to this question is to study schizotypy, or, in the language of DSM-IV, schizotypal personality disorder. The word "schizotype" was first coined by the analyst Rado in 1953 as an abbreviation of the term "schizophrenic phenotype." Meehl later described "schizotaxia" as an integrative neural defect inherited as a single gene, which, given the required triggers, could develop into schizophrenia.

In this edited book, progress in the understanding of schizotypy is reviewed in 18 chapters written by experts in the field. The book ends with an appendix consisting of a discussion of semistructured interviews for the measurement of schizotypal personality disorder. The book is a product of the first international conference on schizotypal personality, held in Italy in 1993. Some of the chapters have been updated since the conference with references from 1994.

The evidence for a genetic link between schizotypy and schizophrenia is reviewed in several chapters. Most studies find a link (although not strong), but a small number of studies do not.

The various scales used in the measurement and establishment of schizotypy are clearly and carefully reviewed. However, the exact definition of schizotypy is still elusive. It has not yet been decided whether the syndrome is most clearly marked by social withdrawal and other "negative" symptoms or by transient "positive" symptoms or, indeed, whether schizotypy can be divided into several syndromes, such as the three-syndrome model suggested by Gruzelier.

Psychophysiological measures of schizotypy, such as skin conductance, the startle reflex, and sensorimotor gating (an elaboration and refinement of the idea of inefficient filtering) are reviewed in detail. The advantages of using tests that are not influenced by learning, motivation, or attention are made very clear, as are the advantages of testing subjects who are not clinically ill or medicated. These advantages also make the tests of more academic than clinical interest.

Claridge and Beech argue that perhaps we make a mistake when we see schizotypy as necessarily pathological. They review a number of experiments in which subjects scoring high in schizotypy performed better than subjects scoring low in schizotypy on some neurocognitive tasks. Enhanced creativity may be the result of the combination of schizotypy and high intelligence.

Other intriguing findings are reviewed. Chapman and Chapman administered five pencil-and-paper scales measuring schizotypy to 7,800 college students. Ten years later, they found that subjects with high scores on the scales measuring perceptual aberration and magical ideation were more likely to develop a DSM-III-R psychosis than were control subjects, but this was not specific for schizophrenia. The high scorers also reported more major depression at follow-up than did the control subjects. This is consistent with some findings of affective disorder in families of subjects with schizotypy, and of schizotypy in the relatives of subjects with affective disorder.

In their introductory chapter, the editors pose overall orienting questions—What is schizotypy? What is its relationship to schizophrenia? As is perhaps appropriate for the first conference on schizotypal personality disorder, the questions remain unanswered by the end of the book. In the final chapter, the editors revisit and refine these questions. The debate between dimensional and categorical approaches is summarized, and the suggestion is made that both approaches may be correct. That is, some schizotypal traits may be categorical, while other traits may be distributed normally throughout the population. The authors also speculate that schizotypal subjects may be seen as individuals who have the genetic predisposition toward schizophrenia but, because of other advantages, do not develop it. These protective factors would be important to describe.

The question of whether schizotypy leads to schizophrenia can be answered only by longitudinal studies (as can the obverse of this question—Is schizophrenia preceded by schizotypy?). Longitudinal studies of at least two groups—relatives of patients with schizophrenia and college students who score high on schizotypy scales—need to be carried out.

The authors (mostly academic psychologists) address these topics with intellectual rigor and great care. Conferences that also review other issues, such as sex differences, comorbidity with such disorders as substance abuse, measures of health service utilization (do schizotypal subjects differ from those without schizotypy in their use of general medical services?), and quality of life issues, should produce equally impressive volumes.