Bob Pearson / EPA Marijuana plants are seen under multi-colored grow lights in the growing rooms at the Denver Discreet Dispensary in Denver, Jan. 1, 2014.

Public support for legalizing marijuana has never been higher, but the latest studies show recreational use is linked with prescription drug misuse.

In the latest nationwide survey [PDF] of 1,501 people polled in mid-March about legalizing marijuana, 52% of those surveyed favored making weed legal, and 72% said that efforts to enforce anti-marijuana laws bring more cost than benefit.

The poll, conducted by the Pew Research Center, also tracked trends in public support for legalization, which has risen dramatically since 1969, when a Gallup poll found only 12% in favor.

The results revealed some interesting trends, including strong generational differences on the question, generally driven by the amount of experience each generation has with the drug. Only 32% of the “Silent” or World War II generation born between 1928 and 1945 favored legal marijuana— and in that age group, only a tiny proportion reported ever trying it. Among Baby Boomers born between 1946 and 1964, who were the first generation to smoke pot in relatively large numbers, 50% supported legalization and around the same proportion had tried the drug.

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Younger respondents from Generation X who came of age in the 1980s and 1990s reported the highest level of youth drug use, with 60% of all high school seniors in 1980 reporting having ever tried marijuana. Xer’s were also the generation targeted by the “Just Say No” anti-drug campaign. Only 28% of this generation favored legalization in 1994— when the media and politicians were heavily focused on fighting the drug war— while 54% now do.

Millennials who were born after 1980 were the most enthusiastic supporters of legalization, with 65% favoring ending marijuana prohibition and only 26% agreeing with the idea that smoking weed is “morally wrong.” In contrast, 48% of the Silent Generation think marijuana use is immoral—although this is down from the 71% among that age group who felt that way in 2006.

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Experience with the drug also seems to play a major role in determining where people stand on the issue. Overall, 70% of those who have tried marijuana think it should be legal, while only 35% of those who haven’t done so favor change. Politically, more Independents and Democrats support legalization, with 60% and 59% in favor respectively, compared to just 37% of Republicans. Interestingly, these divisions narrow dramatically when respondents were asked whether marijuana prohibition is worth the cost: 67% of Republicans, 71% of Democrats and 78% of Independents did not think spending money on enforcing marijuana laws made sense.

One factor that did not seem to influence views on legalization? Whether the survey participants lived in states that had legalized medical marijuana use; views on legalization did not vary in relation to these state laws, although the laws vary dramatically in their control over sales of the drug.

Changing perceptions on whether marijuana is a “gateway” to other drugs did seem to matter, however. In 1990, the Institute of Medicine questioned this notion in an analysis of studies on medical marijuana use and drug abuse rates; the review did not find support for the idea that cannabis physiologically generated a need for more or other illicit drugs. Only 38% of people now agree with the idea that “for most people, the use of marijuana leads to the use of hard drugs” compared to 60% in 1977.

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While marijuana use may not cause use of other drugs, there is an association between pot use and subsequent drug misuse. In the latest study [PDF], based on drug testing results compiled by Quest Diagnostics in 2011 and 2012, researchers analyzed urine samples from more than 200,000 patients that were submitted by physicians who were monitoring use of potentially addictive medications like opioid pain relievers. Because many doctors order tests only when they suspect drug misuse, the results likely do not represent those of typical pain patients or drug users.

In about 60% of the samples tested, either additional drugs that were not prescribed were found, or medications that were prescribed and should have been present were not found. In 42% of these samples that were inconsistent with the doctors’ prescriptions, the tests did not find evidence of prescribed medications.

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Among those with such inconsistent test results, 26% of samples were positive for marijuana, and 45% of those samples also showed nonprescribed pain medications or sedatives in their urine. By comparison, 36% of those who did not use marijuana also tested positive for drugs, primarily sedatives and pain medications, that were not prescribed.

And medical marijuana users were no more — or less — likely to have inconsistent urine results than those who did not report medical marijuana use. This parallels previous research that showed therapeutic use of potentially addictive drugs like marijuana carried less risk for addiction than recreational use.

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So what does this association mean? Studies find that marijuana users are at least twice as likely to misuse other drugs. But the data suggests that this correlation reflects users’ desire to try new and different substances, rather than a drive to seek out the same feelings brought on by marijuana. As the Institute of Medicine report discussed:

People who enjoy the effects of marijuana are, logically, more likely to be willing to try other mood-altering drugs than are people who are not willing to try marijuana or who dislike its effects. In other words, many of the factors associated with a willingness to use marijuana are, presumably, the same as those associated with a willingness to use other illicit drugs.

Teasing apart how trends such as marijuana use and prescription drug misuse are connected will require more, and more detailed, research to better understand how each affects and influences the other, as well as other factors that could contribute to the association. That’s especially important for drug policy, given that more Americans than ever before favor legalization of marijuana.