Using Marijuana May Not Raise the Risk of Using Harder Drugs (but look at alternative explanation)

RAND's Drug Policy Research Center ^ | December 2, 2002 | RAND's Drug Policy Research Center

[unspun]

Using Marijuana May Not Raise the Risk of Using Harder Drugs

Marijuana is widely regarded as a "gateway" drug, that is, one whose use results in an increased likelihood of using more serious drugs such as cocaine and heroin. This gateway effect is one of the principal reasons cited in defense of laws prohibiting the use or possession of marijuana. A recent analysis by RAND's Drug Policy Research Center (DPRC) suggests that data typically used to support a marijuana gateway effect can be explained as well by a different theory. The new research, by Andrew Morral, associate director of RAND Public Safety and Justice, Daniel McCaffrey, and Susan Paddock, has implications for U.S. marijuana policy. However, decisions about relaxing U.S. marijuana laws must necessarily take into account many other factors in addition to whether or not marijuana is a gateway drug.

Support for the Gateway Effect

Although marijuana has never been shown to have a gateway effect, three drug initiation facts support the notion that marijuana use raises the risk of hard-drug use:

• Marijuana users are many times more likely than nonusers to progress to hard-drug use.

• Almost all who have used both marijuana and hard drugs used marijuana first.

• The greater the frequency of marijuana use, the greater the likelihood of using hard drugs later.

This evidence would appear to make a strong case for a gateway effect. However, another explanation has been suggested: Those who use drugs may have an underlying propensity to do so that is not specific to any one drug. There is some support for such a "common-factor" model in studies of genetic, familial, and environmental factors influencing drug use. The presence of a common propensity could explain why people who use one drug are so much more likely to use another than are people who do not use the first drug. It has also been suggested that marijuana use precedes hard-drug use simply because opportunities to use marijuana come earlier in life than opportunities to use hard drugs. The DPRC analysis offers the first quantitative evidence that these observations can, without resort to a gateway effect, explain the strong observed associations between marijuana and hard-drug initiation.

New Support for Other Explanations

The DPRC research team examined the drug use patterns reported by more than 58,000 U.S. residents between the ages of 12 and 25 who participated in the National Household Surveys on Drug Abuse (NHSDA) conducted between 1982 and 1994.^[1] Using a statistical model, the researchers tested whether the observed patterns of drug use initiation might be expected if drug initiation risks were determined exclusively by

• when youths had a first opportunity to use each drug

• individuals' drug use propensity, which was assumed to be normally distributed^[2] in the population

• chance (or random) factors.

To put it another way, the researchers addressed the question: Could the drug initiation facts listed in the first section of this brief be explained without recourse to a marijuana gateway effect?

Figure 1—Probabilities of Initiating Hard Drugs, Marijuana Users and Nonusers

The research team found that these associations could be explained without any gateway effects:

• The statistical model could explain the increased risk of hard-drug initiation experienced by marijuana users. Indeed, the model predicted that marijuana users would be at even greater risk of drug use progression than the actual NHSDA data show (see Figure 1).

• The model predicted that only a fraction of hard-drug users would not have tried marijuana first. Whereas in the NHSDA data 1.6 percent of adolescents tried hard drugs before marijuana, the model predicted an even stronger sequencing of initiation, with just 1.1 percent trying hard drugs first.

• The modeled relationship between marijuana use frequency and hard-drug initiation could closely match the actual relationship (see Figure 2).

The new DPRC research thus demonstrates that the phenomena supporting claims that marijuana is a gateway drug also support the alternative explanation: that it is not marijuana use but individuals' opportunities and unique propensities to use drugs that determine their risk of initiating hard drugs. The research does not disprove the gateway theory; it merely shows that another explanation is plausible.

Figure 2—Probabilities of Hard-Drug Initiation, Given Marijuana Use Frequency in the Preceding Year

Some might argue that as long as the gateway theory remains a possible explanation, policymakers should play it safe and retain current strictures against marijuana use and possession. That attitude might be a sound one if current marijuana policies were free of costs and harms. But prohibition policies are not cost-free, and their harms are significant: The more than 700,000 marijuana arrests per year in the United States burden individuals, families, neighborhoods, and society as a whole.

Marijuana policies should weigh these harms of prohibition against the harms of increased marijuana availability and use, harms that could include adverse effects on the health, development, education, and cognitive functioning of marijuana users. However, the harms of marijuana use can no longer be viewed as necessarily including an expansion of hard-drug use and its associated harms. This shift in perspective ought to change the overall balance between the harms and benefits of different marijuana policies. Whether it is sufficient to change it decisively is something that the new DPRC research cannot aid in resolving.

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^[1]In subsequent years, respondents have not been asked about their first opportunity to use various drugs.

^[2]That is, some people have a high or low propensity, but most people have a propensity near the middle of the range.

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RB-6010 (2002)

RAND research briefs summarize research that has been more fully documented elsewhere. This research brief describes work done in RAND's Drug Policy Research Center, a joint endeavor of RAND Public Safety and Justice and RAND Health. The research is documented in "Reassessing the Marijuana Gateway Effect" by Andrew R. Morral, Daniel F. McCaffrey, and Susan M. Paddock, Addiction 97:1493-1504, 2002.

Abstracts of RAND documents may be viewed at www.rand.org. Publications are distributed to the trade by NBN. RAND^® is a registered trademark. RAND is a nonprofit institution that helps improve policy and decisionmaking through research and analysis; its publications do not necessarily reflect the opinions or policies of its research sponsors.

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[unspun]

Well, agree with some of your revulsion, if not ad hominem sentiments.

...redefine morals and ethics DOWN by giving both of those words little value in their limited vocabulary.

I'd particularly feature this statement. I believe this is a consequense of taking an "objectivist" view of ethics and morality. A part of the fundamental discrepancy between American political philosophy and much of libertarian thought is that the former is based upon self-evident truths (including natural law theory of law) while the Ayn Rand style libertarian tries to look only at cause and effect (something unnatural and counterintuitive and prone to resistance and breakdown even in their own minds).

[tacticalogic]

I'd particularly feature this statement. I believe this is a consequense of taking an "objectivist" view of ethics and morality.

Have you considered the potential ramifications of making ethics and morality subjective?

[unspun]

Have you considered the potential ramifications of making ethics and morality subjective?

IMHO, they are what they are, objective to us and subjective for us to God. But they may be ascertained by subjective means as well as objective. In any case, they are proven as they apply to law, by the taste of the pudding. There, the more objective, the better, but not at the risk of cutting them off from subjective considerations.

How's that for a walk around the yard?

[tacticalogic]

It sounds like you are opposed to an objectivist view of morality and ethics only to the degree, and insofar as it interferes with defining them according to your own subjective standards.

[unspun]

...maybe so! ;-` Except that my plea is that they are not my standards. Someone else owns them, to whom I am accountable in my interpretation.

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I suppose that could be called objectivity* subject to the Author.

*as distinct from objectivism

[A CA Guy]

I agree.
That is a great example of how the smoking laws in California came about.
Thanks, great point!

[tacticalogic]

Except that my plea is that they are not my standards. Someone else owns them, to whom I am accountable in my interpretation.

All well and good. But I think that if you propose that we base our laws, particularly federal laws on those interpretations, and seek agreement from us, then you are accountable to us in that interpretation.

[unspun]

Yes!

And that's reflected that in the Constitution's bottom line, our friendly state legislatures hold the blueprints.

(And beneath the bottomm line, the People hold both ballots and guns.)

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I'm also saying that America has been very negligent its adherence to the Constitution (in holding to it, and in bringing it along, very stingily with us).

[tacticalogic]

I think there's a little more to it than that, if we're going to arrive at a workable solution.

[unspun]

Yeah - but that's details.

[tacticalogic]

The details better include some objective reasons, or people are going to view it as arbitrary. People have a tendency to rebel against arbitrary laws and regulations, and this is not a bad thing, IMHO.

[tacticalogic]

Feeling smarmy today, eh?

[tacticalogic]

I suppose that could be called objectivity* subject to the Author.

*as distinct from objectivism

Apparently the solution to the dilema is to simply make objectivity subjective.

[unspun]

Objective reasons, truly.

Objectivity, as much as is in our power.

[tacticalogic]

Objectivity, as much as is in our power.

Aye. Yet none of us is capable of being truly objective on every subject. The best we can hope for is to be able to recognize the areas and circumstances where we are not, and act accordingly.

[unspun]

..act accordingly, by adhering to the principles that are gained from our experience (all kinds of experience) and applied and tested and adjusted, according to the full set of wisdom and knowledge that we may seek and acquire.

[tacticalogic]

act accordingly, by adhering to the principles that are gained from our experience (all kinds of experience) and applied and tested and adjusted, according to the full set of wisdom and knowledge that we may seek and acquire.

And what should we do in those instances that call for the application of wisdom and knowlege that we have chosen not to seek and acquire?

[unspun]

Then, it's acquired nevertheless.