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 (Golan, 2016). On the x-axis you can see an increasing amount of medication being tested and on the y-axis you can see 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. 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 indicate 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 (Phillips, Turk & Forney, 1971, and Brill et al, 1970).
More recently, the American Medical Association confirmed that it is theoretically possible to die from a marijuana overdose, however, a person would need to smoke 1500 pounds within 15 minutes (Annas, 1997). Given this significant margin of safety, the authors concluded 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 I drug (substances, or chemicals defined as drugs with no currently accepted medical use and a high potential for abuse) to that of a Schedule II 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.
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 that is then watched 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 (McLaren, Swift, Dillon & Allsop, 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, 2016). But new chemical compounds are constantly being manufactured. The effects, like the ingredients, often vary, and users may present to an emergency room with rapid heart rate, vomiting, and negative mental responses, including hallucinations, after using these substances (NIDA, 2016).
According to a 1999 report by the Institute of Medicine (IOM; now the Health and Medicine Division of the National Academies), marijuana’s adverse effects are “within the range of effects tolerated for other medications.” This is not to say that marijuana is completely without adverse effects, especially when consumed in uncontrolled circumstances. There are chronic effects related to THC and chronic smoking. Marijuana smoking, as with all smoking, may be associated with increased risk of cancer and lung damage (IOM, 1999). The primary adverse effect of acute marijuana use is identified as diminished psychomotor ability. People should be advised not to operate heavy equipment or vehicles when under the influence of marijuana, THC, or any cannabinoid drug. Some people also experience dysphoria (a feeling of unease, discomfort, and generalized dissatisfaction). According to the IOM report (1999), older people with no previous experience with taking marijuana often experience psychological effects that are disturbing to them, such as disorientation after being treated with THC. These effects appear to be felt more with oral THC than smoked marijuana. In 2001, researchers who interviewed 3,882 survivors of myocardial infarction (MI) found that the risk for developing MI was 4.8 times higher than average within the hour immediately after marijuana use (Mittleman, Lewis, Maclure, Sherwood, & Muller, 2001). After MI, mortality is significantly higher in marijuana users than in the general population (Thomas, Kloner, & Rezkalla, 2014). On the other hand, a recent study of 5,113 adult participants’ coronary artery risk found no association with the incidence of cardiovascular disease from cumulative lifetime or recent use of marijuana (Reis et al., 2017).
A study of women who smoked marijuana at least once a month during pregnancy found impaired placental development, as indicated through analysis of human tissue obtained at about 7 weeks of gestation. It also found that CB1 and CB2 were decreased in the placenta of marijuana smokers as compared to pregnant nonsmokers (Chang et al., 2017). Marijuana use during pregnancy has been associated with low birth weight and increased risk of both brain and behavioral problems in babies (NIDA, 2017a). Some THC can get into breast milk if a mother is using marijuana regularly (NIDA, 2017a).
As each state re-examines the legal status of marijuana, healthcare professionals may be compelled to re-examine marijuana and their own roles in supporting use in self-care and professional health care. This re-examination does not necessarily mean that healthcare providers will change their opinions. However, reflection is a natural response to mounting public inquiry of health professionals as marijuana use grows exponentially. Contemporary beliefs about marijuana run the gamut from prohibition to social promotion. Some consider marijuana, when compared with alcohol, to be “benign.” Others are concerned that marijuana may serve as a “gateway” drug. Still others ask why people seek the escape of a “high” in the first place. The existential issues of substance use and misuse are just as important with marijuana as with any other drug. Although concerns over marijuana’s use, misuse, and global market may have been to a certain degree eclipsed by the current focus on the “opioid crisis,” its impact continues to be reported by the U.S. National Institute on Drug Abuse and the UNODC that concludes the following:
Research has shown that, notwithstanding the usefulness of some cannabinoids in the management of specific medical conditions, their use, particularly in the botanical form of herbal cannabis with unknown content and dosage, can be detrimental to health. To protect human health, it is therefore necessary that the principles of safety, quality and efficacy and the rigorous scientific testing and regulatory systems that apply to established medicines be applied also to cannabis-based medicines. (UNODC, 2017b, p. 29)
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