FEW ET AL.
Cannabis Involvement and Nonsuicidal Self-Injury: A Discordant Twin Approach LAUREN R. FEW, PH.D.,a JULIA D. GRANT, PH.D.,a ELLIOT C. NELSON, M.D.,a TIMOTHY J. TRULL, PH.D.,b RICHARD A. GRUCZA, PH.D.,a KATHLEEN K. BUCHOLZ, PH.D.,a KARIN J. H. VERWEIJ, PH.D.,c NICHOLAS G. MARTIN, PH.D.,d DIXIE J. STATHAM, D.PSYCH.,e PAMELA A. F. MADDEN, PH.D.,a ANDREW C. HEATH, D.PHIL.,a MICHAEL T. LYNSKEY, PH.D.,f & ARPANA AGRAWAL, PH.D.a,* aDepartment
of Psychiatry, Washington University School of Medicine, St. Louis, Missouri of Psychological Sciences, University of Missouri, Columbia, Missouri cDepartment of Biological Psychology, VU University Amsterdam, Amsterdam, The Netherlands dQIMR Berghofer Medical Research Institute, Herston, Queensland, Australia eSchool of Social Sciences, University of the Sunshine Coast, Sippy Downs, Queensland, Australia fAddictions Department, Institute of Psychiatry, Psychology & Neuroscience, King’s College London, London, United Kingdom bDepartment
ABSTRACT. Objective: Cannabis use, particularly at an early age, has been linked to suicidal thoughts and behavior, but minimal work has examined the association between cannabis use and lifetime nonsuicidal self-injury (NSSI). The current study aims to characterize the overlap between lifetime and early cannabis use and NSSI and to examine genetic and environmental mechanisms of this association. Method: Adult male and female twins from the Australian Twin Registry (N = 9,583) were used to examine the odds of NSSI associated with lifetime cannabis use and early cannabis use (i.e.,