Sex and gender in schizophrenia

Using data collected in a study of sex differences in schizophrenia, I undertook this study to show the utility of distinguishing between sex and gender in the study of schizophrenia. Schizophrenia and schizoaffective disorder were combined to yield 213 patients (141 men, 72 women). There were 98 healthy controls (41 men, 57 women). The relative contributions of sex and gender to the prediction of age of first hospitalization and neuropsychological functioning were examined in linear regression analyses.

Sex, but not gender, was a significant predictor of age at first hospitalization, even when controlling for illness severity. Among patients, sex and gender significantly contributed to the prediction of neuropsychological performance, beyond the contributions of education, age, and illness severity. Comparable results were found among healthy controls, although gender was significant only for women. For both healthy subjects and patients, more frequent endorsement of female typical social roles predicted better neuropsychological functioning.

Being female also predicted higher neuropsychological scores in patients. The findings suggest that some aspects of schizophrenia study, such as the disorder's onset, may be best pursued from a more biological (sex difference) perspective, while a sociocultural (gender difference) perspective may best serve other aspects of study, such as neuropsychological functioning.

The study of sex differences has yielded helpful insights into and stimulated research of the possible role of biopsychosocial processes in the genetic liability, onset, course, etiology, and treatment of schizophrenia. Goldstein and Lewine (2000) recently summarized the sex differences literature, suggesting that men, relative to women, have an earlier onset of illness; a more severe form of the disorder as reflected in greater social, cognitive, and affective impairment; and a poorer long-term outcome but may have a less familial form of the disorder than women. The utility of "sex" as a study variable inheres in its functioning as an uncontaminated predictor variable (Pekorny and Overall 1970) and its relative lack of ambiguity when operationalized by secondary sex characteristics. This line of research has tended to lead to hypotheses about the importance of biological processes in the onset and course of schizophrenia, in particular hypotheses about estrogen. As recently emphasized by Nasser et al. (2002), however, "sex" and "gender" have been used interchangeably in this area of study, as suggested by Lewine (1994).

This causes a problem, as "sex" is primarily a biological variable while "gender" encompasses a broad range of biological, psychological, social, and cultural processes. To benefit maximally from the clues about schizophrenia yielded by "sex differences" research, it is imperative that we distinguish between the two, as they suggest potentially different paths of research.

Not all view "gender" the same way. Some include presumed etiology, while others do not (Unger and Crawford 1993). Gentile (1993), for example, has proposed a terminology to capture explicit assumptions about etiology: "biologically sex-linked" traits for those related to biological femaleness/maleness; "gender-linked" traits for those related to sociocultural processes; "sexand gender-linked" traits for those involving the conjunction of biological and sociocultural factors; and "sex-correlated" traits for those of unknown origin.