title: A clinical comparison of schizophrenia with and without pre-onset cannabis use disorder: a retrospective cohort study using categorical and dimensional approaches.
abstract: BACKGROUND
  A high prevalence of cannabis use disorder has been reported in subjects suffering from schizophrenia, fuelling intense debate about whether schizophrenia with pre-onset cannabis use disorder may be a distinct entity with specific features or whether cannabis use disorder can precipitate schizophrenia in genetically vulnerable subjects.
  
  
  METHODS
  We retrospectively assessed schizophrenia subjects with and without pre-onset cannabis use disorder on the basis of their clinical features, assessed categorically and dimensionally with the operational criteria checklist for psychotic illnesses (OCCPI). We also investigated whether the two groups could be differentiated on the basis of a history of psychiatric disorders in first-degree relatives. A principal component factor analysis of the OCCPI items was used to identify specific symptom dimensions. The relationships between symptom dimensions and cannabis status were analysed by point-biserial correlation analysis to control for sex and age at time of the assessment and illness duration.
  
  
  RESULTS
  One hundred and seventy-one subjects with a diagnosis of schizophrenia were included. Among them, forty-one patients (18.2 % of the sample) had a cannabis use disorder before or at the time of the onset of schizophrenia. We found similar results in symptoms patterns or family history between patients with and without pre-onset cannabis use disorder.
  
  
  CONCLUSIONS
  Our results clearly argue against cannabis-associated schizophrenia being a relevant distinct clinical entity of schizophrenia with specific features.
authors.affiliation: AP-HP, DHU PePSY, Hôpitaux universitaires Henri-Mondor, Pôle de Psychiatrie et d'Addictologie, 94000 Créteil, France ; INSERM U955, Equipe 15, IMRB, 94000 Créteil, France.
authors.forename: Samuel
authors.initials: S
authors.lastname: Sarrazin
authors.affiliation: AP-HP, DHU PePSY, Hôpitaux universitaires Henri-Mondor, Pôle de Psychiatrie et d'Addictologie, 94000 Créteil, France.
authors.forename: Florence
authors.initials: F
authors.lastname: Louppe
authors.affiliation: AP-HP, DHU PePSY, Hôpitaux universitaires Henri-Mondor, Pôle de Psychiatrie et d'Addictologie, 94000 Créteil, France.
authors.forename: Raphael
authors.initials: R
authors.lastname: Doukhan
authors.affiliation: AP-HP, DHU PePSY, Hôpitaux universitaires Henri-Mondor, Pôle de Psychiatrie et d'Addictologie, 94000 Créteil, France ; INSERM U955, Equipe 15, IMRB, 94000 Créteil, France ; Faculté de Médecine, Université Paris-Est, 94000 Créteil, France ; FondaMental Fondation, Fondation de coopération scientifique, 94000 Créteil, France.
authors.forename: Franck
authors.initials: F
authors.lastname: Schürhoff
keywords: Cannabis; OCCPI; Psychosis; Schizophrenia; Symptom dimension