America is struggling to win its battle against drug addiction. The good weather doesn’t help.

Teenagers are more likely to experiment with recreational drugs for the first time during the summer months in part due to the amount of free time on their hands after school finishes in June and activities like music festivals, according to research published Tuesday by the NYU School of Medicine. More than one-third (34%) of teens tried LSD for the first time in the summer, followed by marijuana (30%), ecstasy (also known as MDMA or Molly; 30%) and cocaine (28%).

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“First-time users may be unfamiliar with the effects of various drugs, so it is important to first understand when people are most likely to start these behaviors,” said Joseph Palamar, an associate professor in the Department of Population Health at NYU School of Medicine and the study’s senior investigator. In 2017, more than 3 million people in the U.S. tried LSD, marijuana, cocaine, or ecstasy for the first time, according to federal figures.

The study was published online in the peer-reviewed Journal of General Internal Medicine, and gleaned data collected from the Department of Health and Human Services’ National Survey on Drug Use and Health between 2011 and 2017 involving about 394,415 people ages 12 and older. Participants were surveyed about their use of various drugs through a computer-assisted interview. New users were asked to recall the month and year when they initiated use.

“Parents and educators who are concerned about their kids need to educate them year-round about potential risks associated with drug use,” said Palamar, who is also a researcher in the Center for Drug Use and HIV/HCV Research at NYU College of Global Public Health. “Just say no,” however, is not enough. He said parents should educate and warn their kids about using recreational drugs, their risks and side effects. Heat stroke and dehydration, for example, are two high risks with the dance drug ecstasy.

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Teens have other problems to deal with, too. Teenagers smoking e-cigarettes has also been described as an epidemic that now affects approximately 3.6 million underage users of Juul and other e-cigarettes, the Associated Press reported. Federal law prohibits the sale of these vaping products to minors (those under the age of 18). However, 1 in 5 five high-school students said they had vaped at least once in the previous month, according to 2018 federal survey figures.

Opioids also remain a persistent threat. People addicted to drugs are buying them on the street, as drugs like heroin are now often cheaper than prescription opioids. People sometimes develop an addiction to pain medication after being prescribed opioids for an injury or ailment, experts say.