title: Indications of a dose-response relationship between cannabis use and age at onset in bipolar disorder.
abstract: Cannabis use seems to play a causal role in the development of psychotic disorders. Recent evidence suggests that it may also precipitate onset in bipolar disorder. We here investigate if there is a dose-response relationship between cannabis use and age at onset in bipolar disorder, and whether there are interactions between cannabis use and illness characteristics (presenting polarity and presence of psychosis). Consecutively recruited patients with a DSM-IV, SCID verified diagnosis of bipolar I, II or NOS disorder (n=324) participated. Two-way ANCOVAS were used to investigate the effect of levels of cannabis use (<10 times during one month lifetime, >10 times during one month lifetime or a cannabis use disorder) on age at onset, including interaction effects with illness characteristics, while controlling for possible confounders. There was a significant association indicating a dose-response relationship between cannabis use and age at onset, which remained statistically significant after controlling for possible confounders (gender, bipolar subtype, family history of severe mental illness and alcohol or other substance use disorders). There were no interaction effects between cannabis use and presenting polarity or presence of psychosis. Doses of cannabis used may affect the age at onset of bipolar disorder.
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway. Electronic address: t.v.lagerberg@medisin.uio.no.
authors.forename: Trine Vik
authors.initials: TV
authors.lastname: Lagerberg
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Levi Røstad
authors.initials: LR
authors.lastname: Kvitland
authors.affiliation: Division of Mental Health Services, Akershus University Hospital, Lorenskog, Akershus, Norway.
authors.forename: Sofie R
authors.initials: SR
authors.lastname: Aminoff
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Monica
authors.initials: M
authors.lastname: Aas
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Petter Andreas
authors.initials: PA
authors.lastname: Ringen
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Ole Andreas
authors.initials: OA
authors.lastname: Andreassen
authors.affiliation: NORMENT Centre for Psychosis Research, Oslo University Hospital and Institute of Clinical Medicine, University of Oslo, Oslo, Norway.
authors.forename: Ingrid
authors.initials: I
authors.lastname: Melle
mesh_terms: D000293:Adolescent; D000328:Adult; D017668:Age of Onset; D000368:Aged; D001714:Bipolar Disorder / Q000175:diagnosis / Q000209:etiology*; D039721:Diagnostic and Statistical Manual of Mental Disorders; D005260:Female; D006801:Humans; D008297:Male; D008385:Marijuana Smoking / Q000009:adverse effects*; D008875:Middle Aged; D012307:Risk Factors; D055815:Young Adult
keywords: Presenting polarity; Psychosis; Risk factor; Substance use