Document is current

Article History

Received: 21 January 2017

Accepted: 14 August 2017

First Online: 22 August 2017

Ethics approval and consent to participate

: This analysis was conducted according to the guidelines and procedures involving human subjects approved by the University of Washington Institutional Review Board. All twins enrolled in the Washington State Twin Registry (formerly the University of Washington Twin Registry) provided informed consent to participate in the Registry according to the guidelines and procedures involving human subjects originally approved by the University of Washington Institutional Review Board with continuing review by the Washington State University Institutional Review Board.

: Not applicable.

: The authors declare that they have no competing interests.

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