Weed Potency Hits 30-Year High
Study finds THC levels have doubled since 1983, raising mental health worries
By Rob Quinn,  Newser Staff
Posted Jun 12, 2008 8:11 AM CDT
Health officials worry that the increase in marijuana's potency could lead to more addiction and mental disorders.   ((c) Meepocity)
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(Newser) – 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.