Cannabis and mental health: prevalence of use, modes of administration, and adverse outcomes by past 12-month mental health experience in Canada and the US.

Abstract

Background: Cannabis is among the most widely used drugs in the world. Although it is well established that cannabis may have an adverse impact on certain mental health conditions, there is relatively little data on how patterns of cannabis use differ by mental health status. The primary objective of this study was to examine cannabis use among consumers who reported a past 12-month experience of a mental condition, in regard to five specific outcomes: 1) prevalence of cannabis use; 2) types of products used by consumers; 3) medical help-seeking behaviours from adverse effects of cannabis use; 4) patterns of specific adverse health effects experienced; and 5) perceived impact of cannabis on friendships, physical health, mental health, family life, social life, work, and quality of life.

Methods: Data came from the 2018 International Cannabis Policy Study (Wave 1). Online surveys were conducted from Aug 27- Oct 7, 2018 with respondents aged 16-65 from Canada and the US. In Study 1, multinomial regression models examined differences in cannabis use prevalence (no use in the past 12 months/less than monthly/weekly or monthly/daily) among cannabis consumers with and without self-reported past 12-month experience of anxiety, depression, PTSD, bipolar disorder, and psychosis/schizophrenia. Binary logistic regression models tested differences in use of nine cannabis product types (dried herb, oils (oral/vaped), edibles, drinks, concentrates, hash, tinctures, topicals). In Study 2, binary logistic regression models examined differences in medical help-seeking, as well as adverse health effects reported by consumers (nausea, heart problems, dizziness, panic, hallucinations, flashbacks, depression, dissociation). In addition, multinomial models examined seven outcomes related to perceived impact of cannabis use (friendships or social life, physical and mental health, family life, work, studies, quality of life).

Results: In Study 1, respondents with each of the five mental health conditions reported more frequent cannabis use than those without a mental health condition (p<.01). Past 12-month cannabis consumers who experienced mental health conditions were also significantly more likely than those without a mental health condition to use the most potent products (solid concentrates, THC vape oils, and hash; p<.05), with fewer differences for dried flower, edibles, orally ingested oils, and other forms. In Study 2, 4.3% of past 12-month consumers reported seeking medical help for an adverse effect of cannabis, particularly for panic, dizziness, and nausea/vomiting. Medical help-seeking was greater among those who experienced psychosis (22.4%: OR= 5.48; 3.20-9.37), bipolar disorder (9.4%: OR= 2.32; 1.44-3.74), and depression (6.0%: OR=1.71; 1.28-2.27). Additionally, 41.5% reported using cannabis to manage symptoms of mental health, with the highest rates among those with bipolar disorder (90.6%) and psychosis (90.8%). Consumers reporting >1 mental health condition were more likely to perceive positive impacts of cannabis use for each of the 7 categories (friendships or social life, physical and mental health, family life, work, studies, quality of life; p<.001 for all), whereas consumers with psychosis were most likely to perceive negative health effects across the 7 categories.

Conclusion: Individuals experiencing mental health conditions report more frequent cannabis use and use of more potent product types, despite public health warnings highlighting the potential risks of cannabis use among those susceptible to mental health conditions. For conditions with substantial evidence suggesting cannabis use is harmful (psychosis, bipolar disorder), greater medical help-seeking behaviours and self-perceived negative effects of cannabis use were observed. Consumers with mental health conditions were more likely to perceive cannabis to have a positive effect on their lives than those without. Thus, the relationship between cannabis use and mental health is complex, disorder specific, and may include a combination of perceived benefits as well as harms.