A puzzling occurrence to many Chinese visiting the United States in the last four years is that marijuana has been legalized by a growing number of states, and the support among the public is also rising.

This is quite a contrast to the fact that most people in China would still associate marijuana with the country's bitter Opium War in the mid-19th century, a war forced by the British to legalize its opium trade in China.

So far, 28 US states and the District of Columbia have allowed legal medical marijuana, and many of them have also allowed recreational use since the states of Colorado and Washington became the first to legalize recreational use in 2012.

A Pew Center survey last October found that 57 percent of US adults say the use of marijuana should be made legal, while 37 percent say it should be illegal. The view a decade ago was the reverse, with just 32 percent favoring legalization and 60 percent opposing it.

Meanwhile, a Gallup poll found that 13 percent (or 1 in 8) of US adults in 2016 said they were using marijuana, while that number was only 7 percent in 2013.

US federal law makes it illegal for the use, possession, sale, cultivation and transportation of marijuana, but the federal government has articulated that if a state passes a law to decriminalize it for recreational or medical use, it can do so under the condition that a regulation system for marijuana is in place.

Marijuana, also called cannabis, grass, weed or pot, is listed as a Schedule I substance by the US Drug Enforcement Administration, along with heroin. The DEA defines a Schedule I drug as a substance that has a high potential of being abused and has no accepted medical uses.

Sanjay Gupta, a CNN medical correspondent, described marijuana as useful in the treatment of cancer, epilepsy and Alzheimer's disease and in reducing pain.

But Stuart Gitlow, former president of the American Society of Addiction Medicine, told a US Senate hearing last July that apathy, lost productivity, addictive disease, deterioration in intellectual function, motor vehicle accidents, and psychosis are all among the negative outcomes.

The debate about marijuana is far from over in the US, and it is far beyond the health and medical realm. A Washington Post report last October, quoting a study by the American Civil Liberties Union and Human Rights Watch, said police make more arrests for marijuana possession than for all violent crimes combined.

US President Barack Obama, former presidents Bill Clinton and George W. Bush and a long list of Democratic, Republican and independent politicians such as Al Gore, Bernie Sanders, Michael Bloomberg, Sarah Palin and Newt Gingrich have admitted to once using marijuana.

While many more US states, such as Vermont, Rhode Island and Missouri, are likely to legalize marijuana, it is still unknown what President-elect Donald Trump's administration will do about it.

Trump spoke of supporting medical marijuana during the campaign, but his pick for attorney general, Jeff Sessions, is well known for opposing the legalization. In last week's confirmation hearing, Sessions said he "won't commit to never enforcing federal law".

The change and debate in the US have not gone unnoticed in China, especially after the August 2014 high-profile arrest in Beijing of American-born Hong Kong actor and singer Jaycee Chan Jo-ming, son of well-known martial artist/actor Jackie Chan. Jaycee Chan was arrested for possessing 3 ounces of marijuana in his apartment.

Jackie Chan, an anti-drug goodwill ambassador in China, admitted to taking drugs for eight years. He repeatedly apologized for his son's drug use. The son was finally released in February 2015 after making a public apology.

Like most countries in the world, possession, sale, transportation and cultivation of marijuana is illegal in China.

In arguing for legalizing marijuana, many Americans have traced its medical use back to ancient China. But in the memory of many Chinese, marijuana is synonymous with opium, a much more potent substance that the British forced upon the Chinese during the Opium War. The war was widely regarded by Chinese as the start of their country's "century of humiliation".

Such a bitter collective memory means it would be much harder for any prospects of legalizing marijuana in China. In 2014, after the arrest of Jaycee Chan, the People's Daily warned that legalizing marijuana would be a disaster for the nation.

To me, the pungent and awful smell from marijuana use increasingly experienced on the sidewalks in Washington is an unpleasant addition to an otherwise beautiful city.

Contact the writer at chenweihua@chinadailyusa.com