Investigating the Dose-Response Relationship Between Cannabis Use and the Onset of Schizophrenia: A Hazy Link

Abstract

Background: Schizophrenia is a psychological disorder that 51 million individuals suffer from globally. This disorder has been speculated to have both biological and environmental origins. Cannabis use has been investigated as a potential risk factor for the development of schizophrenia in a dose-response relationship. Objectives: A structured literature review was conducted to assess the evidence associating quantity of cannabis use and the subsequent development of schizophrenia. To date, hundreds of studies show conflicting evidence regarding the psychological effects cannabis use can exert on the human brain. It is necessary to consolidate these studies due to the impending legalization of cannabis in Canada. Methods: An initial investigation was done using key search terms in SCOPUS, where 73 articles were accessed. Articles were excluded based on language, publication date, the use of multiple illicit substances, inaccessibility and unrelated research objectives. After the exclusion criteria were applied, 6 pertinent articles were analyzed. The reference lists of these articles were searched using the key terms (schizophrenia) and (cannabis), leading to 35 new articles. These articles were subjected to the same exclusion criteria, resulting in 5 additional articles. A total of 11 articles were analyzed. Results: Upon analysis of the selected articles, 9 presented a strong association between cannabis use and onset of schizophrenia, 5 of which specified a dose-response relationship. Conclusion: A strong association between cannabis use and the development of schizophrenia was established. There was little consensus within the articles attributing schizophrenia development to the dosage of cannabis use. In order to formulate a definitive dose-response relationship, further research must be conducted.