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Research paper
Cannabis use is both independently associated with and mediates worse psychosocial health in patients with epilepsy
  1. Sandra Wahby1,
  2. Vikram Karnik1,
  3. Anita Brobbey2,
  4. Samuel Wiebe1,
  5. Tolulope Sajobi1,2,
  6. Colin Bruce Josephson1,2
  1. 1 Clinical Neurosciences, University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada
  2. 2 Community Health Sciences, University of Calgary Cumming School of Medicine, Calgary, Alberta, Canada
  1. Correspondence to Dr Colin Bruce Josephson, Clinical Neurosciences, University of Calgary Cumming School of Medicine, Calgary, AB T2N 2T9, Canada; cbjoseph{at}


Objective To examine whether cannabis use is associated with or mediates psychosocial health in people with epilepsy.

Methods Consecutive adult epilepsy patients visiting the Calgary Comprehensive Epilepsy Programme clinic were administered validated patient-reported outcome measures (PROMs) including the Neurological Disorders Depression Inventory for Epilepsy (NDDI-E), Quality of Life in Epilepsy (QOLIE-10-P), EuroQOL five dimensions five level scale (EQ-5D-5L), Global Assessment of Severity of Epilepsy Scale, Global Assessment of Disability Associated with Seizures Scale and the Treatment Satisfaction Questionnaire for Medication scale. We used multiple regression analyses to investigate associations between cannabis use and PROMs. Mediation analyses were performed to determine the degree to which cannabis modulated the associations between current or past psychiatric disorders, monthly seizure frequency, and 1-year seizure freedom on psychosocial health.

Results Of 337 consecutive patients, 71 (21%) reported cannabis use. Cannabis use was independently associated with depression (NDDI-E score≥14; OR 3.90; 95% CI 2.01 to 7.59; p<0.001), lower quality of life (β=−16.73, 95% CI − 26.26 to − 7.20; p=0.001), worse epilepsy-related disability (OR 2.23, 95% CI 1.19 to 4.17; p=0.01) and lower satisfaction with antiepileptic medication (OR 0.41, 95% CI 0.23 to 0.72; p=0.002). Cannabis use mediates 7%–12% of the effect of a psychiatric history on depression, worse quality of life and worse health valuation.

Conclusions There is a strong and independent association between cannabis use and poor psychosocial health, and it partially mediates the deleterious effect of a psychiatric history on these same outcomes. Inclusion of PROMs in future cannabis trials is warranted.

  • epilepsy
  • cannabis
  • epidemiology
  • health outcomes
  • quality of life

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  • Collaborators Calgary Comprehensive Epilepsy Programme collaborators: Yahya Agha-Khani; Paolo Federico; Alexandra Hanson; Nathalie Jette; William Murphy; Neelan Pillay; Shaily Singh.

  • Contributors CBJ and SWi conceived and designed the study. CBJ, SWi and the Calgary Comprehensive Epilepsy Programme collaborators all contributed to the acquisition of data. CBJ, SWi, SWa, VK, AB and TS all contributed to analysis and interpretation of the data. SWa, VK and CBJ wrote the initial draft of the manuscript and designed the figures. All authors revised it critically for important intellectual content. All authors gave final approval for publication of this version of the manuscript. All authors agree to be accountable for all aspects of the work and ensure that questions related to the accuracy or integrity of any part of the work are appropriately investigated and resolved.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Patient consent for publication Not required.

  • Ethics approval The study was approved by the University of Calgary’s Conjoint Health Research Ethics Board and Alberta Health Services (REB17-0369).

  • Provenance and peer review Not commissioned; externally peer reviewed.

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