Submitted for Publication: September 5, 2013; final revision received December 20, 2013; accepted January 27, 2014.
Published Online: April 23, 2014. doi:10.1001/jamapsychiatry.2014.89.
Study concept and design: Maciejewski, Heath, Verweij.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Maciejewski, Verweij.
Critical revision of the manuscript for important intellectual content: Creemers, Lynskey, Madden, Heath, Statham, Martin, Verweij.
Statistical analysis: Maciejewski, Martin, Verweij.
Obtained funding: Lynskey, Madden, Heath.
Administrative, technical, or material support: Statham.
Study supervision: Creemers, Statham, Verweij.
Conflict of Interest Disclosures: None reported.
Funding/Support: This work was supported by grants AA07535, AA0758O, AA07728, AA10249, AA13320, AA13321, AA14041, AA11998, AA17688, DA012854, DA018267, DA018660, DA23668, and DA019951 from the National Institutes of Health, grants 241944, 339462, 389927, 389875, 389891, 389892, 389938, 442915, 442981, 496739, 552485, 552498, and 628911 from the Australian National Health and Medical Research Council, the Centre for Research Excellence on Suicide Prevention, and grant ZonMW 31160212 from the Netherlands Organization for Health Research and Development.
Role of the Sponsor: The funders had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation, review, or approval of the manuscript; and decision to submit the manuscript for publication.
Additional Contributions: Anjali Henders, QIMR Berghofer Medical Research Institute, Brisbane, Australia, was the project manager, Richard Parker, Soad Hancock, Judith Moir, Sally Rodda, Pieta-Maree Shertock, Heather Park, Jill Wood, Pam Barton, Fran Husband, and Adele Somerville, QIMR Berghofer Medical Research Institute, assisted with data collection, and David Smyth, Harry Beeby, and Daniel Park, QIMR Berghofer Medical Research Institute, provided information technology support. We thank the twins and their families for their participation. No compensation was received from the funders for these contributions.