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Animal Study Supports 'Gateway Theory'

July 14, 2006

A new animal study concludes that adolescent rats given moderate doses of marijuana may be more likely to later self-administer heroin, be more sensitive to the drug, and to give themselves larger doses, Reuters reported July 12.

According to the researchers, the findings support the long-debated "gateway theory" of drug addiction, which holds that youths who experiment with drugs like alcohol or marijuana are more apt to abuse "harder" drugs later in life. "The current findings provide direct evidence in support of the gateway hypothesis that adolescent cannabis exposure contributes to greater heroin intake in adulthood," the study concluded.

Lead researcher Yasmin Hurd of the Mount Sinai School of Medicine in New York said marijuana use appeared to disrupt the reward system in the brain. "Cannabis has very long-term, enduring effects on the brain," she said. "I was really surprised at how specific and enduring the effects of cannabis were."

The research was published online in the journal Neuropsychopharmacology.

Reference:
Ellgren, M., Spano, S. M., Hurd, Y. L. (2006) Adolescent cannabis exposure alters opiate intake and opioid limbic neuronal populations in adult rats. Neuropsychopharmacology, advance online publication 5 July 2006; doi: 10.1038/sj.npp.1301127.