Hall and Solowij state that there is evidence that childhood marijuana use results in diminished scholastic performance and low future work-place achievement (1998, p. 1613). In an NBER working paper, Rosalie Pacula asserts that marijuana plays a direct role in decreasing an individual’s capital creation. According to data compiled from the National Educational Longitudinal Surveys (NELS), Pacula’s analysis of nationalized math and reading test scores from tenth and twelfth graders indicate a fifteen percent drop over time of marijuana users, or a reduction of two percent in future wages for those who do not go to college (Pacula 2005). Pacula puts the statistical effect of adolescent marijuana use into perspective, “the negative impact of marijuana use in the tenth grade on educational attainment is similar in magnitude to the effect of living in a single parent family or living in a family with an income in the lowest quartile” (Pacula 2005).
Indeed, a relationship exists between heavy adolescent marijuana use and poor scholastic and job performance in young adulthood. However, heavy use of marijuana, tobacco, alcohol, and hard drugs in adolescence signals the presence of other risk factors that by themselves diminish scholastic and job performance. Psychologists identify risk factors such as low grade point average, lack of religiosity, early alcohol abuse, low self-esteem, and poor parental relationships as factors which initiate drug abuse and also signal that an individual will continue to have low scholastic and workplace performance (Newcomb, 1986, p. 525). Evidence also suggests that marijuana adversely affects family formation, mental health, and involvement in drug-related crime, but as before, when controlled for other pre-existing factors, this association diminishes (Hall, 1998, p. 1613).
There are many studies that confirm marijuana as an associative variable rather than an explanatory variable for low capital creation and poor school performance. McCaffery et al. analyzed the relationship between persistent marijuana use and dropout rates of high school students in South Dakota. Using weighted regression, they found a positive association between the two variables, but other differences in characteristics and behavior of the individual explained over half of the association (2008, p. 19). The remaining association was statistically insignificant and attributed to parental and peer influences (2008, p. 21). In a similar model, Rosa Duarte, José Julián Escario, and José Alberto Molina also found a relationship between marijuana and student failure rate. Their analysis confirmed that marijuana often appeared as a warning sign that low grades, dropping out, and low future scholastic performance will arise, but adolescent marijuana use appeared as a characteristic that came along with these other behaviors, not as the underlying cause of scholastic underachievement (2006, p. 479).
An adolescent’s decision to use marijuana may signal that he/she may not be scholastically high-achieving, but in most cases, it is not the reason for it. This is not surprising; using an illegal substance at such a young age indicates the presence of other factors that induce early drug use. Environmental and personality factors, not marijuana, best explain why certain adolescents have diminished capital creation.
Marijuana’s potential to influence future hard drug use is another concern raised by legalization proponents. The gateway effect, the theory that an individual will be more likely to use harder drugs after using marijuana, can occur in three ways according to Jeffery DeSimone. First, DeSimone states that marijuana can generate curiosity in other drugs or reduce fears in trying them. Secondly, the individual marijuana user may experience diminishing marginal returns of “euphoria” from continued marijuana use and experiment with other drugs in order to attain their original level of euphoria. And finally, marijuana use can simply be a marker of personal characteristics or unobservable facts that lead one to trying drugs in the first place (1998, p. 149). As marijuana is usually the first illicit drug an individual tries, DeSimone is able to accurately estimate current cocaine demand based on reconstructions of previous marijuana demand. Using the National Longitudinal Survey of Youth from 1984-1988, De Simone calculates past demand levels of marijuana based on previous state laws, beer tax rates, and indicators of parental alcoholism. DeSimone’s results indicate that marijuana use in 1984 increases the probability of cocaine use in 1988 (1998, p. 160). Although marijuana use may predict cocaine use in DeSimone’s model, this association does not prove that marijuana causes future drug use as the gateway theory dictates. While drug users may begin by using marijuana, marijuana’s placement as first in a sequence of drugs does not indicate causation. The difficulty in identifying marijuana use as the underlying reason for future drug use is the largest problem in the gateway hypothesis.
A twin study by Arpana Agrawal et al. from the University of Virginia Institute of Behavioral Genetics assessed this issue of the gateway effect. Researchers attempted to identify the causal effect of marijuana use on future drug dependence when controlling for genetics and shared environments. Agrawal’s results showed that marijuana use strongly predicted future drug use, but when controlled for environmental and genetic factors, this association diminished (2004 p.1235). Agrawal concluded that although marijuana contributed to some causal effect, the main association came from other factors (2004, p. 1235).
The causal effects of marijuana on future drug use are tenuous, and the most logical explanation for the observed “gateway effect” is that marijuana is the first drug that many people try. The RAND Corporation, a global think-tank that provides a considerable amount of research on drug policy, acknowledges that while they do not stand in favor of legalization, their recent marijuana gateway research does not support the theory. Andrew Morral, director of RAND’s Public Safety and Justice unit explains, “People who are predisposed to use drugs and have the opportunity to use drugs are more likely than others to use both marijuana and harder drugs…marijuana typically comes first because it is more available” (www.rand.org). Simply put, marijuana is usually the first illicit drug people use. If in an individual is predisposed to drug use through genetics or environmental factors, then they will begin with the substance that is easiest to get.
Taken as a whole, marijuana’s dizzying array of implicit costs add further complexity to the issue of legalization. Heavy, life-long use of marijuana subtly erodes the mind, and the immediate intoxicating effects of marijuana impair judgment. But despite this, marijuana use lacks power as an explanatory variable in high-school dropout rates, low scholastic achievement, and other hard drug use. Marijuana appears in certain adolescents as a warning sign of future underachievement and drug abuse but cannot overcome the strength of other environmental variables that influence the success of certain individuals. Also, marijuana use at an early age may affect the brain’s chemistry, but the gateway theory’s assertion that it causes further drug use is under heavy skepticism and remains unproven. In terms of legalization, the health and capital effects of marijuana are moderate enough to lend support to either side of the argument.
