Genetic Epidemiology, Translational Neurogenomics, Psychiatric Genetics and Statistical Genetics Laboratories investigate the pattern of disease in families, particularly identical and non-identical twins, to assess the relative importance of genes and environment in a variety of important health problems.
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PMID
25972816
TITLE
A critical assessment of the equal-environment assumption of the twin method for schizophrenia.
ABSTRACT
The classical twin method (CTM) is central to the view that schizophrenia is ~80% heritable. The CTM rests on the equal-environment assumption (EEA) that identical and fraternal twin pairs experience equivalent trait-relevant environmental exposures. The EEA has not been directly tested for schizophrenia with measures of child social adversity, which is particularly etiologically relevant to the disorder. However, if child social adversity is more similar in identical than fraternal pairs in the general twin population, the EEA is unlikely to be valid for schizophrenia, a question which we tested in this study. Using results from prior twin studies, we tested if intraclass correlations for the following five categories of child social adversity are larger in identical than fraternal twins: bullying, sexual abuse, physical maltreatment, emotional neglect and abuse, and general trauma. Eleven relevant studies that encompassed 9119 twin pairs provided 24 comparisons of intraclass correlations, which we grouped into the five social exposure categories. Fisher's z-test revealed significantly higher correlations in identical than fraternal pairs for each exposure category (z ≥ 3.53, p < 0.001). The difference remained consistent across gender, study site (country), sample size, whether psychometric instruments were used, whether interviewing was proximate or distant to the exposures, and whether informants were twins or third persons. Combined with other evidence that the differential intraclass correlation for child social adversity cannot be explained by evocative gene-environment covariation, our results indicate that the CTM does not provide any valid indication of genomic effects in schizophrenia.
DATE PUBLISHED
2015
HISTORY
PUBSTATUS PUBSTATUSDATE
received 2014/11/16
accepted 2015/04/09
entrez 2015/05/15 06:00
pubmed 2015/05/15 06:00
medline 2015/05/15 06:01
AUTHORS
NAME COLLECTIVENAME LASTNAME FORENAME INITIALS AFFILIATION AFFILIATIONINFO
Fosse R Fosse Roar R Division of Mental Health and Addiction, Vestre Viken Hospital Trust , Lier , Norway.
Joseph J Joseph Jay J Clinical Psychologist in Private Practice , Oakland, CA , USA.
Richardson K Richardson Ken K Independent Researcher/Formerly Open University UK , Durham , UK.
INVESTIGATORS
JOURNAL
VOLUME: 6
ISSUE:
TITLE: Frontiers in psychiatry
ISOABBREVIATION: Front Psychiatry
YEAR: 2015
MONTH:
DAY:
MEDLINEDATE:
SEASON:
CITEDMEDIUM: Print
ISSN: 1664-0640
ISSNTYPE: Print
MEDLINE JOURNAL
MEDLINETA: Front Psychiatry
COUNTRY: Switzerland
ISSNLINKING: 1664-0640
NLMUNIQUEID: 101545006
PUBLICATION TYPE
PUBLICATIONTYPE TEXT
Journal Article
Review
COMMENTS AND CORRECTIONS
GRANTS
GENERAL NOTE
KEYWORDS
KEYWORD
classical twin method
equal-environment assumption
intraclass correlations
schizophrenia
social adversities
MESH HEADINGS
SUPPLEMENTARY MESH
GENE SYMBOLS
CHEMICALS
OTHER ID's