One of the worries attached to Washington’s legalization of recreational-marijuana sales and use is that young people could be harmed by it. Actually, the drug is already easy to get, but there may be a shortage of moderating information about it.

Good information exists, but more of it needs to be in people’s hands, at their fingertips and talked about enough to sink in. I’m not advocating 1950s drug-scare drama but a stronger recognition that whatever you put in your body has an impact, and sometimes it may not be an impact you want.

Marijuana changes the brains of young users in detrimental ways, and the more a person smokes, the worse the effect can be. It’s smart to know what the trade-offs are, just as it is for using alcohol, or eating doughnuts.

Times reporter Bob Young, who’s covered every angle of marijuana legalization, has written about concerns over kids using marijuana, and in the most recent story he included a link to a rich resource of information that should be a go-to site for teens, parents and even adult users.

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It’s a fact sheet on the site of the University of Washington Alcohol and Drug Abuse Institute.

I didn’t click on the link in Bob’s story when I read it in April, but I went back to it after a new study published a few days later caught my attention. According to the researchers, their study is the first to show a relationship between casual marijuana use and brain abnormalities in young users.

Scientists already knew that heavy users show brain changes, but some of the students in the study used marijuana only once or twice a week. When their brains were examined with three different neuroimaging methods, the changes showed up.

And where they showed up is important — in brain regions that involved emotion and motivation. The study was a collaboration between Northwestern Medicine and Massachusetts General Hospital/Harvard Medical School.

The students in that study were between 18 and 25 years old. Other studies have shown marijuana use at younger ages can lead to a range of troubles. Any drug use is bad when it is interacting with a young developing brain.

And it’s because children’s brains are still developing that they can so easily make dangerous choices. I’ve seen studies that say young people are often aware of the dangers grown-ups warn them against, but they tend to weigh potential rewards more heavily than potential risks. Put friends in the mix, and making safe choices can be even harder.

But kids aren’t helpless. I’m certain that giving them more information, more often will help them make better choices.

A 2012 survey of Washington students (the Washington State Healthy Youth Survey) found a decline in the percentages of teens who “perceive a great deal of risk of harm in using marijuana regularly.” Students surveyed were in grades 8, 10, and 12.

They need more information.

The UW fact sheet says early and continued use of marijuana can “affect memory, attention and ability to think clearly, making it difficult to concentrate, learn new things, and make sound decisions.” It has been associated with “a moderate decrease in IQ in current heavy users.”

Most teens aren’t heavy users (and fewer than half of high-school seniors in the United States report ever having used marijuana), but the falling perception of risk should be of concern.

Adults need the information to discuss marijuana intelligently with young people, and also because adult use has an impact on children — and not just because of the example it sets.

Pregnant women who use marijuana risk lifelong changes to the brains of the children they are carrying.

And parents who leave unsecured drugs in their homes tempt fate — young children don’t know whether a brownie is just a brownie. Studies have found that unintentional exposure to marijuana, while it doesn’t happen in great numbers, rises when states make marijuana for medical use legal.

Legalizing marijuana solves a criminal-justice problem but can open the door to health and behavioral problems. A more informed public is the best preventive medicine for that.

Jerry Large’s column appears Monday and Thursday. Reach him at 206-464-3346 or