title: Short communication: Genetic association between schizophrenia and cannabis use.
abstract: Previous studies have shown a relationship between schizophrenia and cannabis use. As both traits are substantially heritable, a shared genetic liability could explain the association. We use two recently developed genomics methods to investigate the genetic overlap between schizophrenia and cannabis use.
  
  
  
  Firstly, polygenic risk scores for schizophrenia were created based on summary statistics from the largest schizophrenia genome-wide association (GWA) meta-analysis to date. We analysed the association between these schizophrenia polygenic scores and multiple cannabis use phenotypes (lifetime use, regular use, age at initiation, and quantity and frequency of use) in a sample of 6,931 individuals. Secondly, we applied LD-score regression to the GWA summary statistics of schizophrenia and lifetime cannabis use to calculate the genome-wide genetic correlation.
  
  
  
  Polygenic risk scores for schizophrenia were significantly (α<0.05) associated with five of the eight cannabis use phenotypes, including lifetime use, regular use, and quantity of use, with risk scores explaining up to 0.5% of the variance. Associations were not significant for age at initiation of use and two measures of frequency of use analyzed in lifetime users only, potentially because of reduced power due to a smaller sample size. The LD-score regression revealed a significant genetic correlation of rg=0.22 (SE=0.07, p=0.003) between schizophrenia and lifetime cannabis use.
  
  
  
  Common genetic variants underlying schizophrenia and lifetime cannabis use are partly overlapping. Individuals with a stronger genetic predisposition to schizophrenia are more likely to initiate cannabis use, use cannabis more regularly, and consume more cannabis over their lifetime.
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands; Neuroscience Campus Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands; Behavioural Science Institute, Radboud University, Montessorilaan 3, 6525 HR Nijmegen, The Netherlands. Electronic address: karin.verweij@vu.nl.
authors.forename: Karin J H
authors.initials: KJ
authors.lastname: Verweij
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Abdel
authors.initials: A
authors.lastname: Abdellaoui
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Michel G
authors.initials: MG
authors.lastname: Nivard
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Alberto
authors.initials: A
authors.lastname: Sainz Cort
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Lannie
authors.initials: L
authors.lastname: Ligthart
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands; Neuroscience Campus Amsterdam, De Boelelaan 1085, 1081 HV Amsterdam, The Netherlands.
authors.forename: Harmen H M
authors.initials: HH
authors.lastname: Draisma
authors.affiliation: Department of Biological Psychology/Netherlands Twin Register, VU University, van der Boechorststraat 1, 1081 BT Amsterdam, The Netherlands.
authors.forename: Camelia C
authors.initials: CC
authors.lastname: Minică
authors.forename: Nathan A
authors.lastname: Gillespie
authors.forename: Gonneke
authors.initials: G
authors.lastname: Willemsen
authors.forename: Jouke-Jan
authors.initials: JJ
authors.lastname: Hottenga
authors.forename: Dorret I
authors.lastname: Boomsma
authors.forename: Jacqueline M
authors.initials: JM
authors.lastname: Vink
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D004200:Diseases in Twins / Q000453:epidemiology / Q000235:genetics; D005260:Female; D020022:Genetic Predisposition to Disease / Q000453:epidemiology / Q000235:genetics; D055106:Genome-Wide Association Study / Q000379:methods; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000453:epidemiology* / Q000235:genetics*; D008875:Middle Aged; D020412:Multifactorial Inheritance / Q000235:genetics*; D009426:Netherlands / Q000453:epidemiology; D010641:Phenotype; D012042:Registries; D012559:Schizophrenia / Q000453:epidemiology* / Q000235:genetics*; D055815:Young Adult
keywords: Cannabis; Genetic correlation; Polygenic risk; Quantitative genetics; Schizophrenia