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Weed my lips: The good and not-so-good aspects of cannabis use among patients

Dec. 1, 2021
Despite its growing use, public health concerns regarding cannabis remain. This is especially true among dental hygienists. Why? Because patients have never had such widespread access to a drug that we know so little about.

According to the Drug Enforcement Administration (DEA), cannabis is a Schedule I controlled substance. As such, cannabis is considered to have no accepted medical use and thus, is illegal to possess, like heroin and LSD. Yet, in the decades since the passage of the Controlled Substances Act of 1970, almost every state has enacted some legislation aimed at legalizing or decriminalizing cannabis for medical or recreational use. In 2019, the US House of Representatives passed the Marijuana Opportunity Reinvestment and Expungement Act, also known as the MORE Act of 2020, aimed at removing cannabis from Schedule I of the Controlled Substances Act. 

Since cannabis was a Schedule I controlled substance under federal law at the time, I didn't learn about it in school, and I’ll bet most of you didn’t learn about it either. No one could have anticipated then the political, social, and medical acceptance that cannabis enjoys today. I would surmise that the full extent of cannabis use among Americans is still largely unknown. 

However, despite this meteoric rise in the social and legal acceptance of cannabis, public health concerns regarding its use remain. This is especially true among dental hygienists. Why? Because patients have never had such widespread access to a drug that we know very little about, and because the major routes of administration of this drug all involve the oral cavity. 

In the first installment of this two-part column about cannabis, I will explore the not-so-good aspects of cannabis use among patients. For the most part, these have to do with misconceptions about cannabis’s systemic effects. 

The not-so-good about cannabis 

One common misconception about cannabis is that since it makes a person “mellow,” it should also make someone calm and less anxious. Indeed, a low dose of the active cannabinoid tetrahydrocannabinol (THC) has that effect. Many people who voted for legalization of cannabis may have been thinking about the marijuana distributed during the 1960s to 1980s, which induced these effects. At that time, the THC content of cannabis was low, typically less than 2%. 

However, between 1995 and 2015, there has been a 212% increase in the THC content of cannabis.1 Some products with concentrated forms of cannabis, such as hash and hash oil, can have as much as 80% to 90% THC. Though low doses of THC will likely induce only mild paranoia or social anxiety, large doses can cause exaggerated adverse effects, including dysphoria, agitation, and psychosis. Studies showed that the use of high potency THC of greater than 15% resulted in a three times increased risk of psychosis, and if the use was daily, there was a five times increased risk.1 As you might guess, this is of concern to dental hygienists since these exaggerated adverse effects may lead patients to exhibit inappropriate or unexpected behavior during their appointments. 

Another common and related misconception is that since cannabis, again, makes a person “mellow,” it should also lower pulse and blood pressure. However, cannabis use actually results in elevation of heart rate and blood pressure immediately after use, primarily due to sympathetic nervous system stimulation and parasympathetic nervous system inhibition.2 A growing body of anecdotal evidence is becoming available that indicates cannabis users require more anesthesia.3 Again, this concerns dental hygienists since local anesthesia with epinephrine may exacerbate cannabis-related tachycardia and hypertension and may precipitate cardiac dysrhythmia, especially in patients who may already be hypertensive and tachycardic from the stress of their procedure. 

In addition, while many people believe that cannabis is a natural supplement that can be used to promote overall health and well-being, published research shows that cannabis use may impair immune function.4 Thus, cannabis use may increase the risk of opportunistic infection, such as secondary bacterial infections, oral candidiasis, and human papillomavirus infection, as well as head and neck cancer. It may also impair wound healing after procedures. 

Finally, published research shows that long-term users of high-THC content cannabis dosage forms may develop cannabinoid hyperemesis syndrome (CHS), a condition that leads to repeated and severe bouts of vomiting, as many as 10 to 12 times per day. As experts on oral pathology, orofacial cancer, and the ravages of stomach acid on dentition, dental hygienists are invaluable in tailoring treatment plans, patient management, and providing information and resources about these potential complications of cannabis use.

In part 2 of this article, I focus on the many potential benefits cannabis use may have on patients. 


  1. Stuyt E. The problem with the current high potency THC marijuana from the perspective of an addiction psychiatrist. Mo Med. 2018;115(6):482-486. 
  1. Richards JR, Blohm E, Toles KA, et al. The association of cannabis use and cardiac dysrhythmias: a systematic review. Clin Tox. 58(9):861-869. doi:10.1080/15563650.2020.1743847 
  1. Ruder K. If you smoke pot, your anesthesiologist needs to know. Kaiser Health News. April 2, 2020. https://khn.org/news/if-you-smoke-pot-your-anesthesiologist-needs-to-know/
  2. Maggirwar SB, Khalsa JH. The link between cannabis use, immune system, and viral infections. Viruses. 2021;13(6):1099. doi:10.3390/v13061099
About the Author

Tom Viola, RPh, CCP

With more than 30 years’ experience as a board-certified pharmacist, clinical educator, professional speaker, and published author, Tom Viola, RPh, CCP, has earned the reputation as the go-to specialist for making pharmacology practical and useful for dental teams. He is the founder of Pharmacology Declassified and is a member of the faculty of more than 10 dental professional degree programs. Viola has contributed to several professional journals and pharmacology textbooks, and currently serves as a consultant to the American Dental Association’s Council on Scientific Affairs.