WASHINGTON (Reuters) - For the first time, a majority of Americans back legalizing marijuana, marking significant changes in public opinion toward the drug, especially among the young, a survey by the Pew Research Center showed on Thursday.
The survey showed 52 percent of Americans support legalizing marijuana, which the federal government deems an illegal drug even as many states have loosened restrictions on "pot" use.
Support for legalizing pot has risen by 11 points since 2010 and was up from just 12 percent backing in 1969, when 84 percent of those polled opposed legalization. In the most recent survey, 45 percent of Americans opposed legalization.
"For the first time in more than four decades of polling on the issue, a majority of Americans favor legalizing the use of marijuana," Pew said in a statement.
Colorado and Washington became the first U.S. states to legalize the possession and sale of marijuana for recreational use following twin referendums last November. Nineteen states and the District of Columbia allow the medical use of marijuana.
The Pew poll found that 65 percent of people born since 1980 favor legalizing marijuana use, up from 36 percent in 2008.
Among baby boomers - those born in the two decades after World War Two - 50 percent favor legalizing marijuana, up from a low of 17 percent in 1990.
Some 72 percent of those polled said government efforts to enforce marijuana laws cost more than they are worth. Sixty percent said the federal government should not enforce federal laws barring use of marijuana in states where it is legal.
There are partisan differences over legalization, with 59 percent of Democrats supporting making marijuana legal, compared with 37 percent of Republicans.
But 57 percent of Republicans and 59 percent of Democrats say the federal government should not enforce federal marijuana laws in states that permit its use.
Tom Angell, chairman of Marijuana Majority, an advocacy group, said it was time for politicians to catch up with the public attitude on legalization.
"You're going to start seeing more politicians running toward our movement instead of away from it, just as we've seen happen" with same-sex marriage, he said in an emailed statement.
The Pew survey was conducted March 13-17 among 1,501 adults. The margin of error was 2.9 percentage points.
(Reporting by Ian Simpson and Dave Graham; Editing by Cynthia Johnston and John Wallace)