title: Alcohol confounds relationship between cannabis misuse and psychosis conversion in a high-risk sample.
abstract: OBJECTIVE
  Cannabis use has been examined as a predictor of psychosis in clinical high-risk (CHR) samples, but little is known about the impact of other substances on this relationship.
  
  
  METHODS
  Substance use was assessed in a large sample of CHR participants (N = 370, mean age = 18.3) enrolled in the multisite North American Prodrome Longitudinal Study Phase 1 project. Three hundred and forty-one participants with cannabis use data were divided into groups: No Use (NU, N = 211); Cannabis Use without impairment (CU, N = 63); Cannabis Abuse/Dependence (CA/CD, N = 67). Participants (N = 283) were followed for ≥2 years to determine psychosis conversion.
  
  
  RESULTS
  Alcohol (45.3%) and cannabis (38.1%) were the most common substances. Cannabis use groups did not differ on baseline attenuated positive symptoms. Seventy-nine of 283 participants with cannabis and follow-up data converted to psychosis. Survival analysis revealed significant differences between conversion rates in the CA/CD group compared with the No Use (P = 0.031) and CU group (P = 0.027). CA/CD also significantly predicted psychosis in a regression analysis, but adjusting for alcohol use weakened this relationship.
  
  
  CONCLUSIONS
  The cannabis misuse and psychosis association was confounded by alcohol use. Non-impairing cannabis use was not related to psychosis. Results highlight the need to control for other substance use, so as to not overstate the cannabis/psychosis connection.
authors.affiliation: Division of Psychiatry Research, The Zucker Hillside Hospital, North Shore-Long Island Jewish Health System, Glen Oaks, NY, USA.|Department of Psychiatry, Hofstra/North Shore-LIJ School of Medicine, Hempstead, NY, USA.
authors.forename: A M
authors.initials: AM
authors.lastname: Auther
authors.affiliation: Department of Psychiatry, University of California, San Diego, La Jolla, CA, USA.
authors.forename: K S
authors.initials: KS
authors.lastname: Cadenhead
authors.affiliation: Division of Psychiatry Research, The Zucker Hillside Hospital, North Shore-Long Island Jewish Health System, Glen Oaks, NY, USA.|Department of Psychiatry, Hofstra/North Shore-LIJ School of Medicine, Hempstead, NY, USA.|Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, North Shore-Long Island Jewish Health System, Manhasset, NY, USA.
authors.forename: R E
authors.initials: RE
authors.lastname: Carrión
authors.affiliation: Department of Psychiatry, University of Calgary, Calgary, AB, Canada.
authors.forename: J
authors.initials: J
authors.lastname: Addington
authors.affiliation: Semel Institute for Neuroscience and Human Behavior, University of California, Los Angeles, Los Angeles, CA, USA.
authors.forename: C E
authors.initials: CE
authors.lastname: Bearden
authors.affiliation: Department of Psychology, School of Medicine, Yale University, New Haven, CT, USA.|Department of Psychiatry, Yale University, School of Medicine, New Haven, CT, USA.
authors.forename: T D
authors.initials: TD
authors.lastname: Cannon
authors.affiliation: Department of Psychiatry, Yale University, School of Medicine, New Haven, CT, USA.
authors.forename: T H
authors.initials: TH
authors.lastname: McGlashan
authors.affiliation: Department of Psychiatry, University of North Carolina at Chapel Hill, Chapel Hill, NC, USA.
authors.forename: D O
authors.initials: DO
authors.lastname: Perkins
authors.affiliation: Department of Psychiatry, Harvard Medical School at Beth Israel Deaconess Medical Center and Massachusetts General Hospital, Boston, MA, USA.
authors.forename: L
authors.initials: L
authors.lastname: Seidman
authors.affiliation: Department of Psychiatry, University of California, San Diego, La Jolla, CA, USA.
authors.forename: M
authors.initials: M
authors.lastname: Tsuang
authors.affiliation: Department of Psychology, Emory University, Atlanta, GA, USA.
authors.forename: E F
authors.initials: EF
authors.lastname: Walker
authors.affiliation: Department of Psychiatry, Yale University, School of Medicine, New Haven, CT, USA.
authors.forename: S W
authors.initials: SW
authors.lastname: Woods
authors.affiliation: Division of Psychiatry Research, The Zucker Hillside Hospital, North Shore-Long Island Jewish Health System, Glen Oaks, NY, USA.|Department of Psychiatry, Hofstra/North Shore-LIJ School of Medicine, Hempstead, NY, USA.|Center for Psychiatric Neuroscience, Feinstein Institute for Medical Research, North Shore-Long Island Jewish Health System, Manhasset, NY, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Cornblatt
mesh_terms: D000293:Adolescent; D019973:Alcohol-Related Disorders / Q000453:epidemiology* / Q000523:psychology; D015984:Causality; D015897:Comorbidity; D018450:Disease Progression; D005260:Female; D006801:Humans; D008297:Male; D002189:Marijuana Abuse / Q000453:epidemiology* / Q000523:psychology; D011605:Psychoses, Substance-Induced / Q000453:epidemiology* / Q000523:psychology; D011618:Psychotic Disorders / Q000453:epidemiology* / Q000523:psychology; D018570:Risk Assessment; D012307:Risk Factors; D012309:Risk-Taking; D014481:United States / Q000453:epidemiology; D055815:Young Adult
keywords: alcohol use; cannabis use; clinical high-risk; prodromal states; psychosis; substance use