Marijuana a gateway drug? Understanding the gateway process involves sequence (use of a gateway drug leading to use of hard drugs), association (increased likelihood of hard drug use in those who use marijuana), and, controversially, causation. Researchers have demonstrated that marijuana use tends to occur before use of harder drugs such as cocaine and heroin and that, relative to nonusers, marijuana users are considerably more likely to subsequently report use of hard drugs. However, the evidence that marijuana use exerts a causal influence on the likelihood of using other illicit drugs has been less clear (Agrawal & Lynsky, 2013). Animal studies have shown that exposure to addictive substances like THC can change how the brain responds to other drugs, particularly as regards response-reward mechanisms that can signal addiction behaviors (NIDA, 2021d). This finding suggests that marijuana may potentially be a gateway drug for some users; however, factors other than these biological mechanisms, such as a person’s social environment, are also critical in determining further risk for drug use (NIDA, 2021e). Trends in people’s use of marijuana leading to further drug use can also be explained by marijuana often being one of the more accessible substances, along with alcohol and tobacco (NIDA, 2021e).
According to Miech et al. (2017), since 2013, attending college has become a substantially stronger risk factor for marijuana use. Before 2013, adolescents in college who had never used marijuana by the 12th grade were 17% to 22% more likely to have used marijuana in the past 12 months than were their age peers who were not in college. This higher relative risk steadily increased and more than doubled in the following years to 31% in 2013, 41% in 2014, and 51% in 2015 (Miech et al., 2017). Academic leaders are beginning to consider interventions for marijuana use as they have for binge drinking and other lifestyle choices and behaviors that can affect education, socialization, and health. There are some in, for example, the criminal justice field who now argue that the gateway drug theory is an “unjustified oversimplification of the dynamics of drug use reflecting the interests of certain stakeholder rather than wise social policy” (Kleinig, 2015, p. 971). The drugs are a branch pattern of the issues of the tree and its roots. In this view, lack of or poor parenting, living in the wrong neighborhood, the need to belong, lack of self-esteem, or whatever it is that makes a self- destructive dependence attractive is the actual “gateway.”
THE EFFECTS OF MARIJUANA
Is marijuana safe? Figure 1 depicts typical dose-response curves for medications, illustrating the distance between the effective-dose curve and the lethal-dose curve as being the margin of safety (Baca & Golan, 2017; Donaldson et al., 2007). The x-axis shows an increasing amount of medication being tested, and the y-axis shows the response to the medication in the study population from no responders to a 100% response rate. Another name for the margin of safety is the therapeutic index (U.S. National Library of Medicine, 2019). The therapeutic index can be calculated by dividing the lethal dose in 50% of the population studied (LD50) by the effective dose in 50% of the population studied (ED50). The therapeutic index for aspirin is 23:1, whereas the therapeutic index for morphine is 50:1. In other words, morphine may be considered a safer drug than aspirin from a toxicity standpoint because more of the drug is required to be lethal. In the case of marijuana, the therapeutic index is closer to 20,000-40,000:1 (Schaffer Library on Drug Policy, 2018). Evidence from early animal studies and human case reports indicates that the ratio of lethal dose to effective dose is quite large and this ratio is much more favorable than that of many other common psychoactive drugs, including alcohol and barbiturates (Brill et al., 1970; Phillips, Turk, & Forney, 1971). It is theoretically possible to die from a marijuana overdose. However, a person would need to smoke 1,500 pounds of marijuana within 15 minutes (Annas, 1997). In February of 2019, a woman in Louisiana may have died from an overdose of THC inhaled from an electronic cigarette, but the conclusion is controversial (Paton, 2019; Renault, 2019). Given this significant margin of safety, a 1997 editorial in the New England Journal of Medicine suggested that: Federal authorities should rescind the prohibition of the medical use of marijuana for seriously ill patients and allow physicians to decide which patients to treat. The government should change marijuana’s status from that of a Schedule 1 drug [substances or chemicals defined as drugs with no currently accepted medical use and a high potential for abuse] to that of a Schedule 2 drug [substances or chemicals defined as drugs with a high potential for abuse, with use potentially leading to severe psychological or physical dependence] and regulate it accordingly (Kassirer, 1997, p. 337).
Figure 1: Medication Dose-Response Curve
Note . Source: Adapted from Donaldson, M., Chanpong, B., & Gizzarelli, G. (2007). Oral sedation: A primer on anxiolysis for the adult patient. Anesthesia Progress, 54 (3), 118-129. An important risk associated with any plant medicine use is adulteration. The American Botanical Council hosts the Botanical Adulterants Program, in which various industry partners “adopt” an herb and then watch it for quality and purity in the marketplace, along with accidental and intentional adulteration. It has been claimed that marijuana cultivars are greatly increasing in THC potency (ElSohly et al., 2016; McLaren et al., 2008) and that scientific testing of marijuana is needed to monitor potency, contamination, and adulteration to address any potential or actual public health risks. There are also concerns about engineered marijuana-based products. One example is “Spice,” also called “K2,” “herbal incense,” or “fake weed.” This product consists of shredded, dried plant material sprayed with chemicals designed to act on the same brain cell receptors as THC. The chemicals are often much more powerful and unpredictable. Some of these products are labeled “not for human consumption,” and many are now illegal (NIDA, 2018; 2021a). New chemical compounds are constantly being manufactured, however. The effects, like the ingredients, often
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