Will Medical Marijuana Laws Affect Marijuana Use by Young People?

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By Bruce Mirken

One of the great myths about medical marijuana laws -- still aggressively put forward by some opponents of such laws -- is that they lead to an increase in teen marijuana use, supposedly by "sending the wrong message" to young people. Over a dozen years of experience since the first effective state medical marijuana law was enacted have shown unequivocally that this is not the case.

All of the 13 states with medical marijuana laws conduct government surveys of adolescent drug use, and 11 of these laws have been in effect long enough for the surveys to have produced what scientists term "longitudinal" data -- that is, data that trace the progression of teen marijuana use from before enactment of the state's medical marijuana law to the period after the law went into effect. Not one of these states has experienced an increase in youth marijuana use since its medical marijuana law was enacted. In fact, all states have reported overall decreases — exceeding 50% in some age groups.

For example, in Washington state, which passed its law in 1998, marijuana use among all age groups surveyed had dropped dramatically by 2006. In 1998, 28.7% of 12th graders reported using marijuana in the past 30 days. By 2006 this figure had dropped by roughly one quarter, to 21.6%. Among younger teens the drop was even more dramatic, with the rate of past-30-days use dropping from 16.5% to 7.0% among 8th graders -- a decline of well over 50%.

California is particularly noteworthy in this regard. This state passed the first and most loosely-drafted medical marijuana law, Proposition 215, in 1996, and has been the subject of sensational media reports suggesting misuse of the law. But California, too, has seen dramatic drops in teen marijuana use since its medical marijuana law took effect.

The official California Student Survey documents that teen marijuana use in the state was rising in the years leading to Prop. 215's passage. For example, use by 9th graders in the past six months peaked at 34.2% in the 1995-96 survey. In 1997--98 this use rate edged down to 32.5%. In 1999-2000 it plunged to 19.2% and has stayed within one percentage point of that figure ever since. Strikingly, the state commissioned a special study of Prop. 215's impact in association with the 1997-98 survey, which found "no evidence supporting that the passage of Proposition 215 was associated with higher rates of marijuana use" among California teens -- but the state declined to formally publish or publicize these findings, over the objections of the researchers.

After more than 12 years of real-world experience with state medical marijuana laws, the results are in, and they are unequivocal. There is simply no evidence that medical marijuana laws have caused an increase in teen marijuana use anywhere

One final note: In order to bolster their argument despite a lack of evidence, some proponents of the "wrong message" theory have resorted to misleading uses of statistics. Some, for example, have cited figures showing that, on average, marijuana use rates in medical marijuana states tend to be somewhat higher than in states without medical marijuana laws. But it is axiomatic among scientists that such "cross-sectional" data -- data that represent a snapshot in time rather than following changes over a period of years -- cannot demonstrate cause and effect. To infer cause and effect from such figures is as ludicrous as claiming that belief in Islam causes drought, since so many Muslim nations have desert climates. But at this point, such logical absurdities are all that proponents of the "wrong message" theory have left.