Changes in patient health questionnaire (PHQ-9) scores in adults with medical authorization for cannabis

Round et al. BMC Public Health (2020) 20:987 https://doi.org/10.1186/s12889-020-09089-3 RESEARCH ARTICLE Open Access Changes in patient health questionnaire (PHQ-9) scores in adults with medical authorization for cannabis Jessica M. Round1, Cerina Lee1, John G. Hanlon2,3, Elaine Hyshka1, Jason R. B. Dyck4 and Dean T. Eurich1* Abstract Background: Legal access to medical cannabis is increasing world-wide. Despite this, there is a lack of evidence surrounding its efficacy on mental health outcomes, particularly, on depression. This study assesses the effect of medical cannabis on Patient Health Questionnaire (PHQ-9) scores in adult patients between 2014 and 2019 in Ontario and Alberta, Canada. Methods: An observational cohort study of medically authorized cannabis patients in Ontario and Alberta. Overall change in PHQ-9 scores from baseline to follow-up were evaluated (mean change) over a time period of up to 3.2 years. Results: 37,338 patients from the cohort had an initial PHQ-9 score recorded with 5103 (13.7%) patients having follow-up PHQ-9 scores. The average age was 54 yrs. (SD 15.7), 46% male, 50% noted depression at baseline. The average PHQ-9 score at baseline was 10.5 (SD 6.9), following a median follow-up time of 196 days (IQR: 77–451) the average final PHQ-9 score was 10.3 (SD 6.8) with a mean change of − 0.20 (95% CI: − 0.26, − 0.14, p-value < 0.0001). Overall, 4855 (95.1%) had no clinically significant change in their PHQ-9 score following medical cannabis use while 172 (3.4%) reported improvement and 76 (1.5%) reported worsening of their depression symptoms. Conclusions: Although the majority showed no clinically important changes in PHQ-9 scores, a number of patients showed improvement or deteriorations in PHQ-9 scores. Future studies should focus on the parallel use of screening questionnaires to control for PHQ-9 sensitivity and to explore potential factors that may have attributed to the improvement in scores pre- and post- 3-6 month time period. Keywords: Depression, Major depressive disorder, Patient health questionnaire, PHQ-9, Medical cannabis Background The medical use of cannabis has become a world-wide phenomenon – with increasing numbers of jurisdictions allowing patient access to cannabis for a variety of therapeutic interventions [1]. Canadians have had legal access to medical cannabis [2] for its treatment of a variety of health conditions [3], including for the improvement of * Correspondence: 1 School of Public Health, University of Alberta, Edmonton, Alberta, Canada Full list of author information is available at the end of the article mental health outcomes [4–6]. Despite its availability, significant evidence gaps remain, particularly for depression and depression-related health outcomes [7–11]. Indeed, there is a lack of rigorous large-patient cohort studies on medical cannabis that utilize standardized validation tools on determining its impact on mental health [12, 13]. Pre-existing clinical studies and systematic reviews on medical cannabis’ impact on depression and depressionrelated outcomes show mixed results. To date, the most recent clinical recommendations from both Canada and the US (based on the best-available evidence) [14, 15] © The Author(s). 2020 Open Access This article is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons licence, and indicate if changes were made. The images or other third party material in this article are included in the article's Creative Commons licence, unless indicated otherwise in a credit line to the material. If material is not included in the article's Creative Commons licence and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this licence, visit http://creativecommons.org/licenses/by/4.0/. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated in a credit line to the data. Round et al. BMC Public Health (2020) 20:987 report that there is limited evidence on cannabis’ efficacy in improving depression symptoms. Importantly, few studies have directly studied the effect of medical cannabis solely on depression [16–19]. Rather, the majority of studies categorize depression under the broad category of mental health outcomes [5, 20, 21]. Furthermore, the studies on depression are themselves, limited, as very few utilize the Patient Health Questionnaire (PHQ-9) [22] as a gold standard for measuring depression outcomes [19, 23, 24]. Likewise, these studies are predominantly designed with small cohort sample sizes [25], focus on how cannabis consumption may cause/develop depression [26, 27] - rather than improve it [13, 28]; very few differentiate medical cannabis use from nonmedical use [29]; and lastly, studies frequently emphasize the limitations of inferences made between medical cannabis and depression due to contemporaneous use of other drugs or illegal substances amongst participants [13, 30]. Thus, this study was designed to provide clarity of the potential impact of medical cannabis on depression and depression-related health outcomes by measuring changes in patients’ PHQ-9 scores over time. Page 2 of 10 patients at cannabis clinics in Alberta and Ontario, Canada who have been authorized to use medical cannabis. As part of the intake process, each patient seeking medical cannabis meets with a counselor who performs an initial assessment and collects relevant data. All patients must provide sociodemographic information and disclose their primary medical complaints that constitute their rationale for requesting a medical cannabis authorization. In addition, patients completed several validated questionnaires at baseline, including: pain questionnaires [31, 32], the Generalized Anxiety Disorder 7-item (GAD-7) scale [33]; Patient Health Questionnaire (PHQ-9) [22]; and the CAGE Questionnaire Adapted to Include Drugs (CAGE-AID) [34], among others. Informed consent is provided by the patient at the time of first referral, which allows data to be collected and used by the clinics. Following their initial intake interview, the patient is referred to a physician who makes their assessment based on the self-reported information as well as the patient’s health record. All data was released as de-identified data. Patient and public involvement Methods Study design Cohort study of patients in Alberta and Ontario, Canada who were authorized medical cannabis between 2014 and 2019. Study population Inclusion criteria The study population consisted of all adult patients authorized to access medical cannabis (...truncated)