Abstract Background Depression has been cited as a possible confounder, moderator, and mediator of the relationship between cannabis use and suicidal behaviours. We aimed to assess the role of depression in the relationship between cannabis use and suicidal behaviours by systematically reviewing existing literature in the general population. Methods We systematically searched PubMed, Science Direct and PsycArticles from database inception to May 20th 2024, for quantitative observational studies investigating the role of depression in the association between cannabis use and suicidal behaviours. We conducted a meta-analysis to examine the confounding role of depression and search for qualitative arguments in favour of moderating and/or mediating roles of depression....