Weeded out.

• Author: Carroll, Linda
• Position: Science

Scientists are working to settle an old question: Is marijuana addictive?

Research is surging, driven in part by the debate over medical marijuana use. It appears that some 10 to 14 percent of users can become strongly dependent on the drug.

Like other addictive substances, marijuana seems to hijack brain circuitry. Some experts fear that this can have serious consequences for the young, noting that addiction among teenagers is on the rise in some cities as use increases nationwide. And reports have described a withdrawal syndrome that can last several weeks.

"You don't see the severe, acute consequences you get with alcohol or...