Sex differences in concordance rates for schizophrenia: finding or artifact?

Area of Science:

• Psychiatry
• Genetics
• Twin Studies

Background:

• Literature suggests higher schizophrenia concordance in female twins for both monozygotic and dizygotic twins.
• This finding has been questioned due to potential biases in study populations.

Purpose of the Study:

• To re-evaluate the reported sex differences in schizophrenia concordance rates among twins.
• To investigate the influence of hospital sampling methods and societal factors on these findings.

Main Methods:

• Review of historical and contemporary twin studies on schizophrenia.
• Analysis of sampling methodologies, particularly the use of resident hospital populations versus consecutive admissions.
• Consideration of evolving societal roles of women.

Main Results:

• Earlier studies using resident hospital populations reported higher concordance in females.
• This sex difference disappeared when samples were based on consecutive admissions.
• Recent studies show no significant sex difference in concordance rates.

Conclusions:

• The previously reported higher concordance rates for schizophrenia in female twins are likely artifacts of biased sampling.
• Changes in research methods and the changing role of women in society have contributed to the vanishing sex difference.
• Schizophrenia etiology in twins appears consistent across sexes when accounting for methodological and societal factors.