密歇根新闻广播 发育问题少年不易吸食大麻（在线收听）

As more states climb aboard the legal weed train, there are voices from the medical community urging caution, especially when it comes to teens. They warn that adolescent brains are exposed to a much more potent form of cannabis than the pot of days gone by.

Dr. Staci Gruber is a clinical neuroscientist in the School of Psychiatry at Harvard Medical School. She studies just how marijuana affects the brain, and she's been watching what's been happening in the states where marijuana was first legalized, like Colorado and Washington State.

What we find from a number of different studies is that early, frequent exposure to cannabis may result in some longer-term or some later difficulties with tasks relative to people who didn't necessarily have the same amount of exposure, or who were exposed later, said Dr. Gruber.

Her concerns about teen consumption of marijuana goes beyond just the THC potency of modern products. Gruber is also worried about the fact that teens today see marijuana as much less risky than they once did. The Healthy Youth Survey conducted by the state of Washington found there has been a significant decrease in the teenage risk perception of cannabis relative to alcohol and tobacco.

While adults may be able to consume marijuana products without significant long-term consequences, however, Gruber says the developing brain of a teenager is far more vulnerable. That heightened risk can be hard to convey to a teenager who sees the adults around them using marijuana for medical or recreational purposes.

How do we let kids understand that this may be a problem when their parents or grandparents may be using cannabis, and in some cases, the very same product? asked Gruber.

There's still relatively little data available on how marijuana impacts things like cognition, sleep, or quality of life. Gruber's Marijuana Investigations for Neuroscientific Discovery (MIND) is trying to change that. But given the unknowns, Gruber says it is safer for adolescents to hold off on using cannabis.

It's not about just say no, it's about saying just not yet, Gruber added.