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As shown in Figure 1, as of January 1, 2016, 21 states 1 have decriminalized certain marijuana possession offenses ( NCSL 2016a), 26 states have legalized medical marijuana use, and another 16 states have adopted cannabidiol (CBD)-only laws ( NCSL 2016b) that protect only certain strains of marijuana to be used for medicinal purposes. Consider for example the state of marijuana policies in the United States at a single point of time. This has resulted in a spectrum of marijuana liberalization policies across the United States that is often not fully recognized or considered when conducting evaluations of recent policy changes. State decriminalization policies were first passed in the 1970s, patient medical access laws began to get adopted in the 1990s, and more recently states have been experimenting with legalization of recreational markets. Although the federal law has prohibited the use and distribution of marijuana in the United States since 1937, for the past five decades states have been experimenting with marijuana liberalization polices.
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