While stemming the opioid use epidemic has dominated the fight against substance abuse in Suffolk County in recent years, the concurrent, ongoing push to legalize recreational marijuana in New York State has created a different challenge for parents and children, who are getting mixed messages about the use of pot. The contention that opioid use can be lethal goes largely unchallenged. But whether marijuana is harmful can depend on factors such as the age of the person using it, according to Kym Laube, program director for SAFE in Sag Harbor, a coalition of parents, educators, businesspeople, and other professionals from various sectors of the village, Noyac, and North Haven.“What I worry about regarding marijuana is there is this perceived low risk if it’s legal — as in, ‘If it’s legal, what’s the harm?’ ” Ms. Laube said. “But one point we always talk to people about, as an organization, is there is no safe use for alcohol or marijuana or nicotine in young, developing brains. The brain in adolescents grows the fastest it grows in a person’s lifetime. We also know the brain doesn’t fully finish growing and hardwiring until the average age of 25 for men and women.” “When you add the use of a chemical [like marijuana] that has the potential to change brain chemistry in an ongoing fashion, what you really have is a recipe for disaster. Yet many parents still look at marijuana use casually, same as they do alcohol.”SAFE in Sag Harbor, SAFE referring to Substance Abuse-Free Environment, is a nonprofit that works in conjunction with Human Understanding and Growth Services, or HUGS, a provider of recreational and educational programs for young people. A federal grant funds SAFE’s activities.Part of SAFE in Sag Harbor’s mission is to challenge the idea of “What’s the harm? What’s the big deal?” said Danielle Laibowitz, the group’s project coordinator and the mother of three children.“We don’t take a formal position on the legalization of marijuana,” Ms. Laibowitz said, stressing that her group is not a political organization. “But we do want people to be informed.”According to Sag Harbor School District survey data, 51 percent of the students in grades 11 and 12 reported that they have tried marijuana (as do 29 percent of ninth and 10th graders). Over all, alcohol use ranks number one among Sag Harbor teens, marijuana use is number two, and vaping is third.Sixty percent of the high schoolers also said there is no perceived risk to marijuana. SAFE in Sag Harbor says some research tells a different story.The National Institute on Drug Abuse, for example, has found that marijuana’s negative effects on memory, attention, and learning can last for days or weeks, and impair focus, concentration, and the ability to execute complex tasks. The institute’s teen website, teens.drugabuse.gov, has reported that a study following people from age 13 to 38 found that those who used marijuana in their teens had up to an eight-point drop in I.Q.To help people make educated decisions, SAFE in Sag Harbor has sponsored various community education efforts. It holds parent workshops and teen leadership gatherings at which alcohol, drug, and nicotine use is discussed. The group has produced public service announcements that recently began running on local cable television stations. Volunteers have staffed tables at events such as Sag Harbor’s HarborFrost celebration and the recent Stories From Suffolk opioids forum in Southampton that was organized by Suffolk County Executive Steve Bellone. During the four-hour forum, marijuana was barely mentioned.SAFE in Sag Harbor is also conducting a direct mailing campaign to all 6,000-plus residents in the 11963 Sag Harbor ZIP code. It features a series of postcards with information and tips on how parents and kids can talk to each other about marijuana use. Five mailings have been done so far, and there are more to come, Ms. Laibowitz said.Some of the messaging is aimed at parents. They are reminded that today’s marijuana is significantly more potent than it was a generation ago, and far more likely to be laced with a range of other substances such as PCP, heroin, or fentanyl. They are also shown how a Columbia University study found that teens who do choose to remain drug-free said their parents were the number-one factor in the decision — something many parents might not know.“What I sometimes hear from my friends is they’re scared their teenage kids won’t communicate with them” if they engage them about drug use, said Tanya Rulon-Miller, a vice president of SAFE in Sag Harbor who has two children under 14. “It gets very complicated the older the children get. Everything I’ve learned is it’s important to start these conversations with kids early, while they’re still kids.” SAFE in Sag Harbor also gives parents tips about how to discuss drug or alcohol use with their children, such as avoiding polarizing words and actions, being a good listener, setting clear expectations and including real consequences, and helping children deal with peer pressure.Ms. Laube said an interesting thing that surfaces in the HUGS/SAFE in Sag Harbor workshops is how parents who don’t approve of under-age drinking or drug use often report feeling peer pressure themselves — from other parents.“It comes up in every parent workshop I run,” Ms. Laube said. “Those parents say they feel they’re in the minority. And they have a hard time being ‘that’ parent. The other parents challenge me on it all the time, too. They’ll say, ‘Kids are going to do it anyway. Better to let them drink in our basement, where I can keep an eye on them.’ ”But Ms. Laube insists that retort misses some important points. Research has shown that people who start with alcohol or marijuana are indeed more likely to try other drugs.“One of the biggest misses we are having right now as a culture is we continue to form task groups around the drug of the day,” she said, “and we’re not talking enough about the disease of addiction itself — we’re talking about substances instead.” If New York does legalize recreational marijuana, communities do have some choice in the matter. The bill being proposed by Gov. Andrew M. Cuomo permits cities and counties with more than 100,000 residents to opt out of allowing retail sales.East Hampton Village Mayor Paul F. Rickenbach Jr. is among the public officials who have urged Mr. Bellone to have Suffolk County exercise that option. As the bill reads now, East Hampton, like Sag Harbor, could not opt out unilaterally.