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Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study

BMJ 2002; 325 doi: (Published 23 November 2002) Cite this as: BMJ 2002;325:1212
  1. Louise Arseneault, lecturera,
  2. Mary Cannon, Wellcome Trust advanced fellowb,
  3. Richie Poulton, director, Dunedin multidisciplinary health and development studyc,
  4. Robin Murray, professorb,
  5. Avshalom Caspi, professora,
  6. Terrie E Moffitt, professor (
  1. a SGDP Research Centre, King's College, London SE5 8AF
  2. b Division of Psychological Medicine, King's College
  3. c Dunedin Multidisciplinary Health and Development Research Unit, University of Otago, Dunedin, New Zealand
  1. Correspondence to: T E Moffitt

    Papers pp 1195, 1199

    The strongest evidence that cannabis use may be a risk factor for later psychosis comes from a Swedish cohort study which found that heavy cannabis use at age 18 increased the risk of later schizophrenia sixfold. 1 2 This study could not establish whether adolescent cannabis use was a consequence of pre-existing psychotic symptoms rather than a cause. We present the first prospective longitudinal study of adolescent cannabis use as a risk factor for adult schizophreniform disorder, taking into account childhood psychotic symptoms3 antedating cannabis use.

    View this table:

    Association between cannabis use in adolescence and schizophrenia and depressive symptoms and disorders at age 26 (n=759), controlling for childhood psychotic symptoms and use of other drugs in adolescence

    Methods and results

    The Dunedin multidisciplinary health and development study (a study of a general population birth cohort of 1037 individuals born in Dunedin, New Zealand, in 1972-3)4 has a 96% follow up rate at age 26. It obtained information on psychotic symptoms at age 11 and drug use at ages 15 and 18 from self reports and assessed …

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