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Cannabis: monitor policy changes

Policy changes that increasingly permit the medical and recreational use of cannabis have important implications for society and drug policies overall (see Nature 524, 280–283; 2015 and Nature 525, S1–S18; 2015). There is an urgent need to set up collaborative international monitoring of the effects of these changes in different countries to achieve a meaningful evaluation of their impact.

Monitoring should include differences in arrest numbers, imprisonment, public-health and social impact, supply and economic analyses, as well as co-dependence and substitution effects on the use of other drugs, alcohol and tobacco products (

The effects of cannabis policy changes might be influenced by, for example, a legal age limit, accurate labelling of contents and potency, restrictions on advertising, and law-enforcement practices.

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Correspondence to Lucas Wiessing.

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Wiessing, L. Cannabis: monitor policy changes. Nature 527, 305 (2015).

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