PORTLAND — The nationwide trend toward legalization of marijuana is making it harder for health care and law enforcement officials to fight the nation’s most dangerous drug problem — rampant abuse of prescription opioids, the Obama administration’s senior advisor on drug policy said.

Despite activists’ insistence that marijuana is harmless, one in nine marijuana users will become addicted to pot and early use of marijuana increases the likelihood that users will develop dependency on other drugs including prescription opioids and heroin, said Michael Botticelli, acting director of the White House’s Office of National Drug Control Policy.

“It’s hard to say at one level that we want to think about prescription drug abuse and heroin abuse without looking at how to prevent kids from starting to use other substances from an early age,” he said.

Botticelli traveled to Maine lead a town hall forum on opioid abuse Wednesday evening in Bangor, where he was formally announcing that 19 Maine communities are getting $7.5 million over the next five years to fight drug abuse. On Thursday, he planned to visit a recovery community center in Portland.

His visit to the state came less than a month before voters in South Portland and Lewiston will decide whether to join Maine’s largest city in legalizing marijuana for recreational use by adults.

Marijuana advocates are hoping to use the municipal referendums as stepping stones to a statewide vote to join Washington and Colorado in adopting statewide legalization of marijuana.

Those laws send a message to students that marijuana isn’t dangerous despite data that shows people who use smoke cigarettes, drink alcohol or use marijuana at an early age are much more likely to suffer addiction as an adult.

Botticelli, who himself battled addiction years ago, said he was introduced to alcohol at an early age and battled alcoholism before giving it up more than 20 years ago. “My personal story is very illustrative of what we see with people who go on to significant addiction later in life,” he told The Associated Press.

Maine has been grappling with the problem of prescription drugs for years, starting with a wave of Oxycontin and Oxycodone abuse in Washington County that evolved into a serious prescription abuse problem statewide.

The prescription drug problem led to dozens of pharmacy robberies in 2012 and 2013; at the same time, the state is dealing with a resurgence of heroin, drug officials said. In 2011, the MDEA investigated 69 heroin cases. In 2012, that jumped to 223 cases.

Botticelli said prescription drug abuse and heroin abuse are intertwined. Many substance abusers start with prescription drugs before moving onto heroin, so that where officials need to focus their efforts, he said.