A central business district (CBD) is the commercial and business center of a city. In larger cities, it is often synonymous with the city's "financial district". Geographically, it often coincides with the "city centre" or "downtown", but the two concepts are separate: many cities have a central business district located away from its commercial or cultural city centre or downtown.
Research suggests that CBD may exert some of its pharmacological action through its inhibition of fatty acid amide hydrolase (FAAH), which may in turn increase the levels of endocannabinoids, such as anandamide, produced by the body. It has also been speculated that some of the metabolites of CBD have pharmacological effects that contribute to the biological activity of CBD.
Personal health also depends partially on the social structure of a person's life. The maintenance of strong social relationships, volunteering, and other social activities have been linked to positive mental health and also increased longevity. One American study among seniors over age 70, found that frequent volunteering was associated with reduced risk of dying compared with older persons who did not volunteer, regardless of physical health status. Another study from Singapore reported that volunteering retirees had significantly better cognitive performance scores, fewer depressive symptoms, and better mental well-being and life satisfaction than non-volunteering retirees.
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There is certainly a need to utilize available germplasm sources in order to breed suitable cultivars for North America. A list of the 24 approved cultivars for the 2001 season in Canada is at www.hc-sc.gc.ca/hpb-dgps/therapeut/htmleng/hemp.html. Most of these are regulated by the European Organization of Economic Cooperation and Development (OECD). These cultivars are “approved” for use in Canada not on agricultural criteria, but merely on the basis that they meet the THC criterion. Indeed, most of these are unsuitable or only marginally suitable for Canada (Small and Marcus 2000), and only a very few Canadian cultivars to date have been created. In Canada, every acquisition of hemp grown at a particular place and time must be tested for THC content by an independent laboratory and, under the industrial hemp regulations, fields of hemp with more than 0.3% THC may require destruction (a slight degree of flexibility is generally exercised). Importation of experimental hemp lines (i.e. other than the approved cultivars) requires importation licenses (as well as phytosanitary clearance of the shipment by the Canadian Food Inspection Agency), and the importation licenses require an indication that the THC contents are low.
A chief argument that has been advanced in favor of developing hemp as a paper and pulp source has been that as a non-wood or tree-free fiber source, it can reduce harvesting of primary forests and the threat to associated biodiversity. It has been claimed that hemp produces three to four times as much useable fiber per hectare per annum as forests. However, Wong (1998) notes evidence that in the southern US hemp would produce only twice as much pulp as does a pine plantation (but see discussion below on suitability of hemp as a potential lumber substitute in areas lacking trees).
Cannabis use started to become popular in the United States in the 1970s. Support for legalization has increased in the United States and several U.S. states have legalized recreational or medical use. A 2018 Social Science Research study found that the main determinants of such changes in attitudes toward marijuana regulation since the 1990s were changes in media framing of marijuana, a decline in perception of the riskiness of marijuana, a decline in overall punitiveness, and a decrease in religious affiliation.