The association between reasons for first using cannabis, later pattern of use, and risk of first-episode psychosis: the EU-GEI case-control study

EU-GEI WP2 Group, Edoardo Spinazzola, Diego Quattrone, Victoria Rodriguez, Giulia Trotta, Luis Alameda, Giada Tripoli, Charlotte Gayer-Anderson, Tom P Freeman, Emma C Johnson, Hannah E Jongsma, Simona Stilo, Caterina La Cascia, Laura Ferraro, Daniele La Barbera, Antonio Lasalvia, Sarah Tosato, Ilaria Tarricone, Giuseppe D'Andrea, Michela GalatoloAndrea Tortelli, Ilaria Tagliabue, Marco Turco, Maurizio Pompili, Jean-Paul Selten, Lieuwe de Haan, Paulo Rossi Menezes, Cristina M Del Ben, Jose Luis Santos, Manuel Arrojo, Julio Bobes, Julio Sanjuán, Miguel Bernardo, Celso Arango, James B Kirkbride, Peter B Jones, Michael O'Donovan, Bart P Rutten, Jim Van Os, Craig Morgan, Pak C Sham, Isabelle Austin-Zimmerman, Zhikun Li, Evangelos Vassos, Robin M Murray, Marta Di Forti

Research output: Contribution to journalArticlepeer-review


Background: While cannabis use is a well-established risk factor for psychosis, little is known about any association between reasons for first using cannabis (RFUC) and later patterns of use and risk of psychosis.

Methods: We used data from 11 sites of the multicentre European Gene-Environment Interaction (EU-GEI) case-control study. 558 first-episode psychosis patients (FEPp) and 567 population controls who had used cannabis and reported their RFUC.We ran logistic regressions to examine whether RFUC were associated with first-episode psychosis (FEP) case-control status. Path analysis then examined the relationship between RFUC, subsequent patterns of cannabis use, and case-control status.

Results: Controls (86.1%) and FEPp (75.63%) were most likely to report 'because of friends' as their most common RFUC. However, 20.1% of FEPp compared to 5.8% of controls reported: 'to feel better' as their RFUC (χ2 = 50.97; p < 0.001). RFUC 'to feel better' was associated with being a FEPp (OR 1.74; 95% CI 1.03-2.95) while RFUC 'with friends' was associated with being a control (OR 0.56; 95% CI 0.37-0.83). The path model indicated an association between RFUC 'to feel better' with heavy cannabis use and with FEPp-control status.

Conclusions: Both FEPp and controls usually started using cannabis with their friends, but more patients than controls had begun to use 'to feel better'. People who reported their reason for first using cannabis to 'feel better' were more likely to progress to heavy use and develop a psychotic disorder than those reporting 'because of friends'.

Keywords: Cannabis use; path analysis; psychotic disorders.
Original languageEnglish
Pages (from-to)7418-7427
Number of pages10
JournalPsychological medicine
Issue number15
Early online date2 May 2023
Publication statusPublished - Nov 2023


  • Humans
  • Cannabis/adverse effects
  • Case-Control Studies
  • Marijuana Smoking/adverse effects
  • Psychotic Disorders/epidemiology
  • Risk Factors


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