As more states make recreational marijuana legal, researchers fret about short- and long-term health effects.
Marijuana is more popular and accessible in the U.S. than any other street drug. In national surveys, 48 percent of Americans say they have tried it, and 6.5 percent of high school seniors admit to daily use. So it was not too surprising when two states, Washington and Colorado, became the first to legalize recreational marijuana in the November 2012 general election, albeit in limited quantity, for anyone over the age of 21. Activists expect that similar measures will soon win approval in other parts of the country.
Some success with medical marijuana helped to pave the road to wider legalization of pot. Eighteen states and the District of Columbia permit possession and consumption of the drug for medical purposes. Doctors in those jurisdictions may prescribe cannabis to treat or manage ailments ranging from glaucoma—an eye disease in which the optic nerve is damaged—to menstrual cramps. Cancer patients sometimes smoke pot to relieve the pain and nausea brought on by chemotherapy, and some people with the inflammatory disease multiple sclerosis rely on marijuana to ease muscle stiffness.
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