Monkeys on Marijuana Wanted More

N E W   Y O R K,  Oct. 16, 2000 -- A new federal study shows that monkeys will dose themselves with themain active ingredient of marijuana repeatedly. Researchers say this evidence strengthens the theory that people can become addicted to pot and provides a new way to test therapies.

Lab animals will actively dose themselves with most drugs abusedby people, but marijuana has been an exception, said researcherSteven Goldberg of the National Institute on Drug Abuse (NIDA).

Some people might interpret that as suggesting it has littlepotential for addiction, he said. But the new work found thatsquirrel monkeys repeatedly pushed a lever to get injections of themarijuana ingredient THC, Goldberg and colleagues report in theNovember issue of the journal Nature Neuroscience.

The animals pushed the lever about as much as other monkeys didto get cocaine, but Goldberg said that does not necessarily meanmarijuana is as addictive as cocaine in people.

Causes Compulsive Craving

NIDA says marijuana causes compulsive and often uncontrollablecraving and use, despite health and social consequences, and therefore isaddictive.

Not everybody agrees.

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“This drug is not addicting. Clinical experience says that,”said Dr. Lester Grinspoon, a Harvard Medical School emeritusprofessor of psychiatry.

The monkey study doesn’t prove otherwise, said Grinspoon, who ischairman of the board of the NORML Foundation, which promotesmedical use of marijuana and, ultimately, its legalization.

In Goldberg’s experiment, four squirrel monkeys sat throughhour-long test sessions once a day with a tube attached to a vein.When a green light turned on, they could push a lever 10 times toget a THC injection.

They gave themselves up to 30 injections per session, versus oneto four when the tube delivered only water.

In proportion to their body size, the monkeys got about the samedose of THC per injection that a person does with each puff from amarijuana cigarette. The monkeys didn’t show any sign of beingsedated, Goldberg said.