Weed Potency Hits 30-Year High

Today's marijuana is the strongest crop since the heyday of Cheech and Chong, a new study finds. University researchers who analyzed seized samples dating back to the '70s found the level of active ingredient THC hit an average of 9.6% last year, up almost 1% from the year before and more than double the 4% recorded for 1983, the AP reports.

The rise in potency, attributed to new growing techniques, has health officials worried. The  director of the National Institute on Drug Abuse, which funded the study, warned that the stronger weed could trigger changes in the brain leading to addiction and mental illness. A professor who serves as an adviser to a pro-marijuana group said that the danger was overstated, as users tend to adjust to stronger marijuana by smoking less of it. (More marijuana stories.)