Cannabis listed 62 times as medicine in 1899 Merck Manual
greenmedinfo.com
greenmedinfo.com
Ask a physician today whether cannabis should be recommended for anything and the probably most likely answer is "we just don't have enough good studies to know yet".
But in 1937 and 1970, they were really sure about it; they claimed "cannabis is not medically useful for any person with any condition" and nobody successfully argued the medical utility or liberty arguments! They've held that position while curing people with prison: people who are exercising their liberty to risk self-harm in pursuit of happiness. So, now, people in States that haven't yet pursued legalization and automated expungement don't sue suppliers who have insufficient quality control due to prohibition (and tax-free margin inflation) instead of regulation in the interest of public health that upholds our highest values: Equality, Life, Liberty, and the pursuit of Happiness.
How different might things have been had we required evidence-based justification for universal quantifications like "not medically useful for any person with any condition" to be kept on file with the Library of Congress for further review.
An observation-based study that couldn't have been a Randomized Controlled Trial (the "gold standard" for clinical research): "Hypothesizing that marijuana smokers are at a significantly lower risk of carcinogenicity relative to tobacco-non-marijuana smokers: evidenced based on statistical reevaluation of current literature." (2008) https://www.ncbi.nlm.nih.gov/m/pubmed/19004418/
This meta-analysis considered 10,700 studies, threw most out for not meeting the inclusion criteria, and concluded that there is sufficient evidence to recommend cannabis for a number of conditions: “The Health Effects of Cannabis and Cannabinoids: The Current State of Evidence and Recommendations for Research” (McCormick et al. 2017) http://nationalacademies.org/hmd/reports/2017/health-effects...