Author Contributions: Dr Gordon-Larsen had full access to all of the data in the study and takes responsibility for the integrity of the data and the accuracy of the data analysis.
Study concept and design: The, Gordon-Larsen.
Acquisition of data: Popkin, Gordon-Larsen.
Analysis and interpretation of data: The, Suchindran, North, Gordon-Larsen.
Drafting of the manuscript: The, Suchindran.
Critical revision of the manuscript for important intellectual content: The, North, Popkin, Gordon-Larsen.
Statistical analysis: The, Suchindran, Gordon-Larsen.
Obtained funding: Gordon-Larsen.
Administrative, technical, or material support: Popkin, Gordon-Larsen.
Study supervision: North, Gordon-Larsen.
Financial Disclosures: None reported.
Funding/Support: This work was supported by National Institutes of Health grant R01-HD057194.
Role of the Sponsor: The National Institutes of Health had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; or preparation, review, or approval of the manuscript.
Additional Information: This research uses data from Add Health, a program project directed by Kathleen Mullan Harris, PhD, and designed by J. Richard Udry, PhD, Peter S. Bearman, PhD, and Kathleen Mullan Harris, PhD at the University of North Carolina, Chapel Hill, and funded by grant P01-HD31921 from the Eunice Kennedy Shriver National Institute of Child Health and Human Development, with cooperative funding from 23 other federal agencies and foundations. Special acknowledgment is due Ronald R. Rindfuss, PhD, and Barbara Entwisle, PhD, both from the University of North Carolina, Chapel Hill, for assistance in the original design. Information on how to obtain the Add Health data files is available on the Add Health Web site (http://www.cpc.unc.edu/addhealth). No direct support was received from grant P01-HD31921 for this analysis. None of the acknowledged individuals received compensation for their assistance.
Additional Contributions: We thank Linda S. Adair, PhD, and Elizabeth J. Mayer-Davis, PhD, University of North Carolina, Chapel Hill, for their advice and Frances Dancy, BS, University of North Carolina Carolina Population Center for her helpful administrative assistance. No compensation was received.