Center Labels Pot Addictive After Test Monkeys Take Repeated Doses

In a new federal study that researchers say emphasizes the idea that people can get hooked on marijuana and provides a new way to test therapies, monkeys repeatedly dosed themselves with the main active ingredient of pot.

Lab animals will actively dose themselves with most drugs abused by people, but marijuana has been an exception, said researcher Steven Goldberg of the National Institute on Drug Abuse.

The study found that squirrel monkeys repeatedly pushed a lever to get injections of marijuana ingredient THC, Goldberg and colleagues report in the November issue of the journal Nature Neuroscience.

The institute says marijuana causes compulsive and often uncontrollable cravings and use, despite health and social consequences, and therefore it is addictive.

In the test, four squirrel monkeys sat through hourlong test sessions once a day with a tube attached to a vein. When a light turned on, they could push a lever up to 10 times to get a THC injection.

They gave themselves as many as 30 shots per session, versus one to four when the tube gave only water.