Submitted for Publication: June 4, 2013; final revision received September 17, 2013; accepted November 4, 2013.
Published Online: February 26, 2014. doi:10.1001/jamapsychiatry.2013.4166.
Study concept and design: Kendler, Ohlsson, K. Sundquist.
Acquisition of data: J. Sundquist, K. Sundquist.
Analysis and interpretation of data: Kendler, Ohlsson, K. Sundquist.
Drafting of the manuscript: Kendler.
Critical revision of the manuscript for important intellectual content: All authors.
Statistical analysis: Ohlsson.
Obtained funding: Kendler, J. Sundquist, K. Sundquist.
Administrative, technical, or material support: Kendler, J. Sundquist, K. Sundquist.
Study supervision: K. Sundquist.
Conflict of Interest Disclosures: None reported.
Funding/Support: This study was funded by grant RO1 DA030005 from the National Institute of Drug Abuse, grants 2008-3110 and 2008-2638 from the Swedish Research Council, the ALF project grant, and the Swedish Council for Information on Alcohol and Other Drugs.
Role of the Sponsor: The funding sources 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.
Correction: This article was corrected on March 5, 2014, for an error in the legend for Figure 4, and on April 2, 2014, for an error in the Submitted for Publication date.