Teenagers are drinking less alcohol, smoking fewer cigarettes, and using less cocaine and heroin — but they’re smoking more marijuana. That’s according to a new study of over 40,000 students between grades 8 and 12, which also showed an increase in the percentage of teens who think marijuana is perfectly harmless. Researchers have conducted the same study every year since the early 90s, and it’s consistently shown that when fewer teens think weed is dangerous, more of them will take up the habit.

With marijuana restrictions relaxing around the country and more states decriminalizing the drug for medical and recreational purposes, it makes sense that teenagers perceive it as a safer way to get high, especially since there’s no risk of overdose.

But more teenagers toking up isn’t necessarily good news. While weed is less carcinogenic and less addictive than cigarettes, and it’s certainly less dangerous than cocaine and heroin, heavy marijuana usage during adolescence has been linked to an increased risk of schizophrenia and irreversible IQ lossPersistent cannabis users show neuropsychological decline from childhood to midlife. Meier MH, Caspi A, et al. Proceedings of the National Academy of Sciences, USA. 2012 Oct 2;109(40):E2657-64.Neuropsychological functioning in adolescent marijuana users: Subtle deficits detectable after a month of abstinence. Medina KL, Hanson KL, et al. Journal of the International Neuropsychological Society, 2007 Sep;13(5):807-20.Cannabis use in adolescence and risk for adult psychosis: longitudinal prospective study. Arseneault L, Cannon M, et al. British Medical Journal, 2002 Nov 23;325(7374):1212-3.Cannabis and schizophrenia. A longitudinal study of Swedish conscripts. Andréasson S, Allebeck P, et al. Lancet, 1987 Dec 26;2(8574):1483-6.. The reason heavy pot usage is riskier for high school students is because the adolescent brain is still developing, so it’s a lot more vulnerable to the long-term effects of drugs and alcohol use.

The overall drop in drinking, cigarette smoking, and hard drug use is definitely a good thing, but growing marijuana use among high school students is a bit worrisome. Wait until you’re older, kids — your brain will thank you!