While marijuana is not addictive in the way that a drug like crack-cocaine is, heavy use can lead to dependence – defined by the same criteria as for other drugs. About half of those who use pot daily become dependent for some period of time, writes Kevin Sabet, in the 2006 book, "Pot Politics" – and 1 in 10 people in the US who have ever used marijuana become dependent at some time (about the same rate as alcohol). Dr. Sabet was a drug policy adviser in the past two presidential administrations.
He adds that physicians in Britain and the Netherlands – both countries that have experience with relaxed marijuana laws – are seeing withdrawal symptoms among heavy marijuana users that are similar to those of cocaine and heroin addicts. This has been confirmed in the lab with monkeys.
Today's marijuana is also much more potent than in the hippie days of yesteryear. But that doesn't change what's always been known about even casual use of this drug: It distorts perception, reduces motor skills, and affects alertness. When combined with alcohol (not unusual), or even alone, it worsens the risk of traffic accidents.
Would legalization take the violence out of the Mexican drug war?
NORML likes to point out that marijuana accounts for the majority of illicit drug traffic from Mexico. End the illicit trafficking, and you end the violence. But that volume gives a false impression of marijuana's role in crime and violence, says Jonathan Caulkins, a professor at Carnegie Mellon and a drug-policy adviser in the US and Australia.