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May 2004



Marijuana shown not addictive, not gateway

The recent study comparing marijuana use in San Francisco and Amsterdam is a real blow to the drug warriors. Not only did it show that prohibition does not reduce marijuana use, there were a couple of other very interesting things in the study.
The full report is now available online as text and as a pdf with graphs.
I’ve had a little time to look at the study, and I’d like to share two particular tables with you, that go beyond the main reported results of the study.
The first one fairly effectively debunks the myth of marijuana as an addictive drug.

TABLE 1—Trajectories of Overall Career Use:

Pattern Amsterdam
No. (%)
San Francisco
No. (%)
1: declining 17 (7.9) 18 (6.8)
2: escalating 13 (6.0) 17 (6.4)
3: stable 24 (11.1) 5 (1.9)
4: increase/decline 104 (48.1) 133 (50.4)
5: intermittent 7 (3.2) 25 (9.5)
6: variable 51 (23.6) 66 (25.0)
Total 216 (100.0) 264 (100.0)
Claims that cannabis produces addiction or
dependence lead one to expect that many experienced users would report Pattern
2—escalation of use over time. But this pattern was reported by only 6% in both
cities, which means that 94% of respondents had overall career use patterns that did not entail escalation across careers.

This is something that is common sense to those who are familiar with how marijuana works, but it’s an important refutation to the drug warriors’ claims. It also shows the most common way cannabis is used — an increase followed by a decline. People use it for a while and then stop or reduce their use voluntarily — certainly not the trend of a dangerous drug.
Here’s another interesting table from the study. This one focuses on regular cannabis users in the two cities and the degree to which they experiment with other drugs.

TABLE 2—Prevalence of Other Illicit Drug Use, Lifetime and During the Past 3 Months:

  Amsterdam (n = 216) San Francisco (n = 264)
Cocaine 48.1 9.3 73.2 7.5
Crack 3.7 0.5 18.1 1.1
Amphetamines 37.5 1.9 60.4 4.5
Ecstasy 25.5 9.3 40.0 6.4
Opiates 21.8 0.5 35.5 2.7
LTP=Lifetime Prevalence, P3MP=Past 3 Months Prevalence

Note that in the city where prohibition is the rule, there is significantly higher rates of experimentation with other drugs. As opposed to the gateway theory, this indicates that prohibition actually increases the likelihood of using other illicit drugs.
As the study notes:

The “separation of markets,”
in which lawfully regulated cannabis
distribution reduces the likelihood that people
seeking cannabis will be drawn into deviant
subcultures where “hard drugs” also are sold
is one public health objective of Dutch decriminalization.

Looks like their idea works better than ours.
Good stuff. Would like to see the media run with this more, though.

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