This paper accompanies the report Medical use of cannabis and cannabinoids — questions and answers for policymaking and summarises the findings of major systematic reviews of the evidence on the effectiveness and safety of cannabis and cannabinoids when used to treat symptoms of various medical conditions. It provides more detail on topics summarised in the main report, in particular on the sections on the available evidence on the effectiveness of medical use of cannabis and cannabinoids and those on the health risks and potential unintended consequences associated with the medical use of cannabis and cannabinoids.