Correction: This article was corrected online February 23, 2016, to fix incorrect author affiliations for 2 authors.
Study concept and design: Mucci, Hjelmborg, Harris, Penney, Koskenvuo, Holm, Pukkala, Kaprio.
Acquisition, analysis, or interpretation of data: All authors.
Drafting of the manuscript: Mucci, Hjelmborg, Graff, Holst, Möller, Unger, Nuttall, Brandt, Kaprio.
Critical revision of the manuscript for important intellectual content: Mucci, Hjelmborg, Harris, Czene, Havelick, Scheike, Holst, Möller, Unger, McIntosh, Penney, Hartman, Kraft, Parmigiani, Christensen, Koskenvuo, Holm, Heikkilä, Pukkala, Skytthe, Adami.
Statistical analysis: Mucci, Hjelmborg, Scheike, Holst, Möller, Kraft, Parmigiani, Skytthe, Kaprio.
Obtained funding: Mucci, Harris, Czene, Havelick, Koskenvuo, Holm, Adami, Kaprio.
Administrative, technical, or material support: Hjelmborg, Harris, Havelick, Graff, Unger, Nuttall, Brandt, Christensen, Holm, Heikkilä, Pukkala, Skytthe, Adami.
Study supervision: Mucci, Hjelmborg, Holst, Christensen, Koskenvuo, Pukkala.
Conflict of Interest Disclosures: The authors have completed and submitted the ICMJE Form for Disclosure of Potential Conflicts of Interest. Dr Kaprio reported receiving personal fees from Pfizer for serving as a consultant on nicotine dependence from 2012 to 2014. No other disclosures were reported.
Funding/Support: This work was supported by funding from the Ellison Foundation (awarded to Drs Mucci and Adami at the Harvard School of Public Health) and the Nordic Cancer Union (awarded to Dr Kaprio). The Finnish Twin Cohort was supported by grants 213506, 129680, 265240, and 263278 from the Academy of Finland and grant agreement HEALTH-F4-2010-261433 from US BioSHaRE-EU. The Swedish Twin Registry was supported by the Ministry for Higher Education. The Danish Twin Cohort was supported by the Odense University Hospital AgeCare program of the Academy of Geriatric Cancer Research. Data collection and research stemming from the Norwegian Twin Registry is supported, in part, from the European Union’s Seventh Framework Programme and grant agreement HEALTH-F4-2010-261433 from US BioSHaRE-EU. Dr Mucci is a Prostate Cancer Foundation young investigator. Dr Adami received distinguished professor award 2368/10-221 from the Karolinska Institutet. Dr Graff is supported by National Cancer Institute training grants R25 CA098566 and R25 CA112355.
Role of the Funder/Sponsors: The sponsors had no role in the design and conduct of the study; collection, management, analysis, and interpretation of the data; preparation of the manuscript; or decision to submit the manuscript for publication. The sponsors reviewed and approved the manuscript
Group Information: The following individuals are additional collaborators within the NorTwinCan collaboration: Norwegian Institute of Public Health: Julia Isaeva and Thomas Nilsen. University of Helsinki: Tellervo Korhonen. University of Southern Denmark: Ulrich Halekoh.
Additional Contributions: We are grateful to the participants of the twin registries in Denmark, Finland, Norway, and Sweden. We recognize the key contribution of Kristina Glimsjo (Karolinska Institutet) for editorial assistance. Ms Glimsjo received no compensation for her contribution.