title: The relationship between cannabis involvement and suicidal thoughts and behaviors.
abstract: BACKGROUND
  In the present study, we examined the relationship between cannabis involvement and suicidal ideation (SI), plan and attempt, differentiating the latter into planned and unplanned attempt, taking into account other substance involvement and psychopathology.
  
  
  METHODS
  We used two community-based twin samples from the Australian Twin Registry, including 9583 individuals (58.5% female, aged between 27 and 40). The Semi-Structured Assessment of the Genetics of Alcoholism (SSAGA) was used to assess cannabis involvement which was categorized into: (0) no cannabis use (reference category); (1) cannabis use only; (2) 1-2 cannabis use disorder symptoms; (3) 3 or more symptoms. Separate multinomial logistic regression analyses were conducted for SI and suicide attempt with or without a plan. Twin analyses examined the genetic overlap between cannabis involvement and SI.
  
  
  RESULTS
  All levels of cannabis involvement were related to SI, regardless of duration (odds ratios [ORs]=1.28-2.00, p<0.01). Cannabis use and endorsing ≥3 symptoms were associated with unplanned (SANP; ORs=1.95 and 2.51 respectively, p<0.05), but not planned suicide attempts (p>0.10). Associations persisted even after controlling for other psychiatric disorders and substance involvement. Overlapping genetic (rG=0.45) and environmental (rE=0.21) factors were responsible for the covariance between cannabis involvement and SI.
  
  
  CONCLUSIONS
  Cannabis involvement is associated, albeit modestly, with SI and unplanned suicide attempts. Such attempts are difficult to prevent and their association with cannabis use and cannabis use disorder symptoms requires further study, including in different samples and with additional attention to confounders.
authors.affiliation: VU University, Department of Developmental Psychology and EMGO Institute for Health and Care Research, Amsterdam, The Netherlands.
authors.forename: M J
authors.initials: MJ
authors.lastname: Delforterie
authors.affiliation: Addictions Department, Institute of Psychiatry, King's College London, United Kingdom.
authors.forename: M T
authors.initials: MT
authors.lastname: Lynskey
authors.affiliation: VU University, Department of Developmental Psychology and EMGO Institute for Health and Care Research, Amsterdam, The Netherlands.
authors.forename: A C
authors.initials: AC
authors.lastname: Huizink
authors.affiliation: Research Institute of Child Development and Education, University of Amsterdam, Amsterdam, The Netherlands.
authors.forename: H E
authors.initials: HE
authors.lastname: Creemers
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: J D
authors.initials: JD
authors.lastname: Grant
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: L R
authors.initials: LR
authors.lastname: Few
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Glowinski
authors.affiliation: School of Social Sciences, University of the Sunshine Coast, Queensland, Australia.
authors.forename: D J
authors.initials: DJ
authors.lastname: Statham
authors.affiliation: University of Missouri, Department of Psychological Sciences, Columbia, MO, USA.
authors.forename: T J
authors.initials: TJ
authors.lastname: Trull
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: K K
authors.initials: KK
authors.lastname: Bucholz
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: P A F
authors.initials: PA
authors.lastname: Madden
authors.affiliation: QIMR Berghofer Medical Research Institute, Brisbane, QLD, Australia.
authors.forename: N G
authors.initials: NG
authors.lastname: Martin
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA.
authors.forename: A C
authors.initials: AC
authors.lastname: Heath
authors.affiliation: Department of Psychiatry, Washington University School of Medicine, St. Louis, MO, USA. Electronic address: arpana@wustl.edu.
authors.forename: A
authors.initials: A
authors.lastname: Agrawal
mesh_terms: D000328:Adult; D001315:Australia; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000523:psychology*; D008385:Marijuana Smoking / Q000523:psychology*; D059020:Suicidal Ideation; D013405:Suicide / Q000523:psychology*; D013406:Suicide, Attempted / Q000523:psychology*; D014427:Twins / Q000523:psychology; D000092864:Suicide Prevention
keywords: Cannabis use; Cannabis use disorder symptoms; Suicidal thoughts and behaviors