Challenging Dogma


...Using social sciences to improve the practice of public health

Thursday, April 26, 2007

Marijuana: Simply a “Gateway Drug” or a Dismal Terminus? - Michelle Skornicki

During health class, we groaned as we sat through mundane anti-drug lectures, slides with troubling photos of drug addicts and sob stories of the tragic demise of young, sober, successful students. The “marijuana is the gateway drug” message provided a backdrop for each lecture and lingered in our minds as we attacked the world on our own. Used as a scare-tactic, the gateway mantra pervaded our handouts distributed in class, the motivational talks at school-wide assemblies, and advertisements on television.

The intervention in schools and the media that presents marijuana as the “gateway drug” may be inaccurate and applies the health-belief model theory incorrectly. The gateway theory implies that use of marijuana will inevitably open the doors and lead to use of other drugs. The health-belief model suggests that perceived severity, susceptibility, barriers to action, and benefits drive individual action.

In 1994, the Partnership for a Drug-Free America, in cooperation with the National Institute on Drug Abuse (NIDA) and the White House Office of Drug Control Policy, announced a new anti-drug campaign that specifically claimed to target marijuana. However, instead of focusing on the harms of marijuana alone, the campaign’s premise was that reducing marijuana use would be a practical strategy for reducing the use of more dangerous drugs (18). To promote their dubious strategy, they showed that many cocaine users had used marijuana previously instead of showing that many marijuana users go on to use cocaine. The gateway theory they advanced does not correctly project an image of susceptibility. Individuals do not feel vulnerable because the “gateway drug” intervention fails to discourage marijuana use alone. While the barrier to using cocaine and other drugs is effective, the barrier to marijuana itself falls short and does not hinder youths from marijuana experimentation. Anti-drug education approaches that present marijuana as the “gateway drug” also mask the severe consequences of marijuana use alone, and are thus ineffective at combating experimentation and long-term use. Therefore, individuals often lack the intention to refrain from using marijuana, and/or think they can safely continue to use marijuana as long as they do not “pass the gate”.

Controversy over the accuracy over the Gateway Theory
To support the “gateway” drug theory, researchers cite the increased relative risk of hard drug initiation for adolescent marijuana users as compared to non-users. They also emphasize the ordering in adolescents’ initiation of different drug classes (an order from alcohol to marijuana to harder drugs), as well as the strong positive relationship between the frequency of marijuana consumption and the risk of hard drug initiation
(1). Some research provides fairly strong evidence of an association between marijuana and other drug use.

However, these phenomena do not prove the gateway theory. The term “gateway drug” may not even be accurate. Whether there is such a thing as a gateway drug is still very contentious. Even if people who use cocaine or other drugs started with marijuana, research has shown only an association, not a causative effect. Individuals may simply encounter marijuana first, and/or possess particular personality traits that make them more inclined than others to experiment with a variety of illegal drugs. For every 120 people who have ever tried marijuana, there is only one active, regular user of cocaine (2). So only a small percentage of marijuana users go on to become addicts of cocaine or other illegal drugs.

The RAND Drug Policy Research Center used mathematical modeling to show that the gateway effect is not necessary to explain the behavior of adolescent drug use across the country. These researchers found that differences in ages when adolescents have opportunities to use marijuana and hard drugs, and varying willingness among youths to try any drugs could likely explain the associations between marijuana and hard drug use (3). People who either have a predisposition for drug use or simply encounter more drugs and have the opportunity to use them are more likely than others to use any drugs - marijuana, or harder ones. Echoing this idea, a study by Hall et al. explains that some individuals find themselves among peers in certain settings that provide more opportunities to engage in drug experimentation (1, 4, 5).

This epidemiologic concept, called “exposure opportunity” described the increased likelihood that cocaine users in a national cross sectional study in the 90’s had used marijuana in the past. This exposure occurs either at home or within a peer-group setting. While those with no exposure to drugs had roughly a 26% chance of cocaine exposure by 25 years old, among previous alcohol or tobacco users, 75% had a cocaine exposure opportunity (6). These results have implications for further evaluation of the supposed gateway hypothesis; one must consider that once one removes the “drug-seeking” characteristic from analysis, the supposed links between marijuana and other drug use may disappear. The gateway concept is an oversimplification that fails to address the underlying mechanisms that drive the link between marijuana and other drug use.

Nonetheless, educators continue to use gateway theory to combat students’ temptations to use drugs early on in middle school. Youths between the ages of 14 and 18 find themselves in a critical period during which they decide whether to use drugs. Individuals who pass this period and reach 21 are less likely to become addicted (7). Those who decide to use drugs have a general propensity for drugs, while those who pass the critical stage will likely refrain from both marijuana and harder drugs. Underlying personal characteristics and genetic factors may predispose individuals to use a variety of drugs, and account for a large proportion of multi drug abuse and dependence patterns across the country (1, 5, 8-11).

By analyzing such external influences, several studies in twins contest the gateway campaign. For example, Agrawal et al. cite that early marijuana use and subsequent use/dependence/abuse of other illegal drugs results primarily from genetic and environmental factors (9). If anti-marijuana campaigns delivered the message that propensity for drugs may in fact be heritable, then adolescents may perceive increased susceptibility to progression to harder drugs, such as cocaine and heroin.

In contrast to Agrawal’s twin study, a recent study in which marijuana users were twice as likely to use illicit drugs as non-users, found that the gateway effect was primarily responsible. Lessem et al. emphasize that the predictive association between marijuana and other drug use remains after controlling for familial and environmental factors(12). However, they still cannot prove a causal effect. Even in the most robust study, researchers cannot extricate all environmental influences from true causal effects because it is impossible to control for the multitude of factors that impact initiation of illicit drug use (1, 4, 5). And to date there are no epidemiological analyses that directly indicate that the association between marijuana and other drug use is causal, because such controlled experiments cannot be conducted in humans.

Problems with the Health Belief Model’s Barrier to Action and Perceived Susceptibility

Even if the gateway theory is accurate, it does not effectively portray a significant barrier to action. The gateway message states that individuals should not use marijuana because it will lead them to harder drugs and their negative effects; their message is supposed to be a barrier to action. However, the barrier to action is ineffective because adolescents tend to think they can resist temptation to experiment further with other drugs. They assume they can use marijuana without suffering consequences, as long as they refrain from using the other drugs. The gateway argument is so tenuous that adolescents may even display increased desire for experimentation. In fact, a study that investigated the impact of anti-drug campaigns found that not only were the gateway campaigns unsuccessful in changing people’s beliefs, attitudes or intentions, but they actually had the opposite effect than intended; adolescents agreed less with the gateway message and the correlations between the beliefs preached and individuals’ attitudes were weaker (13).

This trend is frightening. Throughout the nineties, adolescent perceptions of the negative effects of marijuana declined, while in turn, marijuana use increased. Fewer individuals fear occasional use (7, 14). This reality points towards the need for more accurate, sensible, and aggressive campaigns. In 2005, 16.5% of 8th Graders in middle schools nation-wide had already used Marijuana (11). In order to prevent marijuana use, policy interventions must not assume that the gateway message is effective.

In order to provide a convincing argument that users of marijuana will suffer severe susceptibility to other illicit drug use, the campaign must make the gateway far less alluring; one must emphasize how difficult it is to avoid further drug experimentation. However, since many adolescents look to their neighbor who may have managed to avoid other drugs, we cannot rely on a haunting depiction of the gateway to compel vulnerable youths to abide by the message. Instead, since adolescents are likely to think they can escape the draw of the gate, anti-drug education should focus on the negative consequences of marijuana use alone.

Lack of Perceived Severity of Marijuana Use Alone

The term “gateway drug” puts emphasis on the negative effects of the drugs that supposedly follow from marijuana use, while neglecting what may happen from marijuana itself. Youths who experiment with marijuana may find it seemingly benign at first and are curious whether other drugs have similar properties. Aspects of physiology and social learning processes may drive individuals to try other illicit drugs. Thus, the point is not that the gateway theory is null, but that the term “gateway drug” puts marijuana in a separate and less important category, which ignores the likelihood that long-term marijuana use produces changes in the brain comparable to those seen after long-term use of other major drugs of abuse such as cocaine, heroin, and alcohol. By shifting the focus to cocaine, heroin, and other drugs, the gateway campaign causes youngsters to perceive benefits of marijuana; they can enjoy the lighter drug because the negative effects come from the harder drugs. As part of our nature, we perform a balancing act of the pros and cons of a particular action. By ignoring negative aspects of marijuana itself, the gateway campaign tips the weight of our subconscious scale to the pro side.

If instead, the focus of the message were the negative consequences of the drug in question, then these upsetting aspects of marijuana would mask the perceived benefits. For example, educators could stress that marijuana may not be what it seems, since it can be laced with other substances. At the same time, they should explain how marijuana affects the body. In the short-term, marijuana use can lead to problems with memory and learning, difficulty in thinking and problem solving, and even loss of coordination and increased heart rate (11). The effects on the heart can be very serious; one study has indicated that a marijuana abuser’s risk of heart attack “more than quadruples in the first hour after smoking marijuana” (15). There are also the social factors that accompany marijuana use, such as perpetual absences from work, because of respiratory illness or indolence (11).

Long-term use of marijuana is associated with changes in the brain similar to those seen after long-term abuse of other major drugs. These may include changes in the activity of nerve cells containing dopamine. Marijuana may also act as a carcinogen (16) and disrupt the immune system in other ways by increasing susceptibility to bacterial infections and tumors. It may lead to birth defects and other unknown outcomes, and can itself be addictive Chronic use also often leads to depression, anxiety, and personal disturbances (11, 17). These types of consequences are absent from the gateway approach.

The shortcomings of the gateway theory have important implications for anti-drug policy in education, the media, and the law. The current policy fails to address high marijuana consumption rates because the concept of a gateway does not scare those who assume they are strong enough to resist temptations to experiment with other drugs.

Emphasizing fearsome realities of the use of marijuana alone will alarm youths more than the concept of an inescapable gateway the pulls marijuana users towards other more dangerous drugs. The notion of a gateway is intangible and most think they will successfully escape it. While a causal link between two drugs may seem plausible, campaigns that focus on concrete, proven facts about marijuana are more likely to dissuade potential users. If the gateway theory takes center stage, listeners will only perceive the severity of the drugs past the gate; whereas, if anti-marijuana campaigns focus on marijuana’s negative effects, individuals will be more likely to avoid it. Potential users will perceive significant severity and susceptibility and a strong barrier to action. With the three negative arms of the health belief model enforced, potential users will dwell more on the dangers of marijuana use than the perceived benefits and may be less likely to use marijuana.

REFERENCES

1. Morral AR, McCaffrey DF, Paddock SM. Reassessing the marijuana gateway effect. Addiction 2002;97:1493-504.

2. National Household Survey on Drug Abuse: Population Estimates 1998. US Department of Health and Human Services: Substance Abuse and Mental Health Services Administration 1999:19-31.

3. Rand. RAND study casts doubt on claims that marijuana acts as "gateway" to the use of cocaine and heroin. RAND News Releases December 2, 2002.

4. Hall WD, Lynskey M. Is cannabis a gateway drug? Testing hypotheses about the relationship between cannabis use and the use of other illicit drugs. Drug Alcohol Rev 2005;24:39-48.

5. Fergusson DM, Horwood LJ. Does cannabis use encourage other forms of illicit drug use? Addiction 2000;95:505-20.

6. Wagner FA, Anthony JC. Into the world of illegal drug use: exposure opportunity and other mechanisms linking the use of alcohol, tobacco, marijuana, and cocaine. Am J Epidemiol 2002;155:918-25.

7. Teens cite illicit drugs as major worry, see marijuana as gateway. Am J Health Syst Pharm 1995;52:2170, 2174.

8. Agrawal A, Lynskey MT, Madden PA, Bucholz KK, Heath AC. A latent class analysis of illicit drug abuse/dependence: results from the National Epidemiological Survey on Alcohol and Related Conditions. Addiction 2007;102:94-104.

9. Agrawal A, Neale MC, Prescott CA, Kendler KS. A twin study of early cannabis use and subsequent use and abuse/dependence of other illicit drugs. Psychol Med 2004;34:1227-37.

10. Lynskey M. An alternative model is feasible, but the gateway hypothesis has not been invalidated: comments on Morral et al. Addiction 2002;97:1505-7.

11. NIDA InfoFacts: Marijuana. Retrieved March 31, 2007 from the National Institute on Drug Abuse: http://www.nida.nih.gov/Infofacts/marijuana.html

12. Lessem JM, Hopfer CJ, Haberstick BC, et al. Relationship between adolescent marijuana use and young adult illicit drug use. Behav Genet 2006;36:498-506.

13. Yzer MC, Cappella JN, Fishbein M, Hornik R, Ahern RK. The effectiveness of gateway communications in anti-marijuana campaigns. J Health Commun 2003;8:129-43.

14. Crundall IA. Student perceptions of the danger of drug use: a factor analysis. J Drug Educ 1992;22:147-53.

15. Mittleman MA, Lewis RA, Maclure M, Sherwood JB, Muller JE. Triggering myocardial infarction by marijuana. Circulation 2001;103:2805-9.

16. Sridhar KS, Raub WA, Jr., Weatherby NL, et al. Possible role of marijuana smoking as a carcinogen in the development of lung cancer at a young age. J Psychoactive Drugs 1994;26:285-8.

17. Brook JS RZ, Brook DW. The effect fof early marijuana use on later anxiety and depressive symptoms. Psychologist 2001:35-39.

18. Preventing Drug Abuse among Children and Adolescents. National Institute on Drug Abuse Accessed 11 April 2007.

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