Cannabis Essentials: Tools for Clinical Practice


Cannabis use in the United States is increasing annually in people of all ages. This increase is fueled by state-level legalization, decreased risk perception, and increased social acceptability. Cannabis and its active components, cannabinoids, have been studied for medical uses and marketed in many commercial forms. Cannabis can impair short-term memory, judgment, and coordination, and there is substantial evidence that it can adversely affect multiple organ systems. Cannabinoids have potential adverse drug interactions with commonly prescribed analgesic, psychotropic, and cardiovascular medications. Current evidence supports cannabinoid use only for a limited number of conditions (chemotherapy-induced nausea and vomiting, specific pain and spasticity syndromes, and certain forms of childhood epilepsy); thus, physicians recommending cannabinoids need to weigh the potential harms vs. perceived benefits. The U.S. Preventive Services Task Force recommends universal screening for unhealthy drug use, including cannabis, in adults 18 years and older. However, the American Academy of Family Physicians does not support this recommendation because of the lack of evidence of benefit in screening patients for unhealthy drug use, except for opioid use disorder. Treatment of cannabis use disorder is largely behavioral and requires a patient-centered, multifaceted approach with a focus on patient education. Pharmacotherapy for cannabis use disorder is limited and experimental. Harm reduction strategies and education about cannabis withdrawal syndrome should be provided to patients. Interpretation of urine drug testing for cannabis is challenging because of the persistence of metabolites for four to five days after a single use and for one month after chronic daily use.

Legalization of cannabis in 36 U.S. states and the District of Columbia has transformed a once illegal drug into an over-the-counter remedy for numerous ailments.1 Cannabis has become a multibillion-dollar industry with approximately 15% of U.S. adults reporting cannabis use in 2017.2 Cannabis risk perception among U.S. adolescents and adults has steadily decreased in the past two decades, accompanied by an annual increase in cannabis use among these populations.24 Between 2002 and 2012, the percentage of adults 18 to 29 years of age reporting cannabis use within the previous year doubled from 10.5% to 21.2%.5 The 2017 Monitoring the Future survey found that the annual prevalence of cannabis use for 12th graders was 37.1%.6



The average THC content of a cannabis joint rose from 1.5% in the 1970s to 8.9% in 2008 and 21% in 2018.

A 2017 national survey showed that 22% of Americans incorrectly believe marijuana is not addictive, and 29% strongly believe that its use can prevent health problems.

Between 2002 and 2012, the percentage of adults 18 to 29 years of age reporting cannabis use within the previous year doubled from 10.5% to 21.2%.

Adolescents are 2 to 4 times more likely than adults to develop cannabis use disorder within two years of use.

THC = tetrahydrocannabinol.

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Clinical recommendationEvidence ratingComments

Patients with a personal or family history of psychotic disorders should avoid cannabis because of an increased risk of psychosis.7,31,32


Systematic review and consistent evidence from RCTs

Cannabis should be avoided in pregnant and lactating patients because of potential risks to the infant.34,35


Expert opinion and consensus guideline

Patients with long-term opioid use should avoid concurrent cannabis use.3840


Evidence from RCTs showing potential for some harm and unclear benefits

Cannabinoids should be considered as a third-line option for neuropathic pain if benefits outweigh risks.41


Consistent evidence from RCTs and systematic reviews

Cannabinoids should be considered as second-line therapy for chemotherapy-induced nausea and vomiting.42


Consistent, moderate-quality evidence from RCTs

Patients with cannabis use disorder should be offered a combination of psychosocial interventions.46


Systematic review

RCT = randomized controlled trials.

A = consistent, good-quality patient-oriented evidence; B = inconsistent or limited-quality patient-oriented evidence; C = consensus, disease-oriented evidence, usual practice, expert opinion, or case series. For information about the SORT evidence rating system, go to

The Author

PAYAM SAZEGAR, MD, FAAFP, FASAM, is a faculty physician in the Kaiser Permanente Family Medicine Residency Program, San Diego, Calif., and an assistant clinical professor in the Department of Family Medicine and Public Health at the University of California San Diego School of Medicine.

Address correspondence to Payam Sazegar, MD, FAAFP, FASAM, Kaiser Permanente San Diego FMR, 6911 Convoy Ct., San Diego, CA 92111 (email: Reprints are not available from the author.

Author disclosure: No relevant financial affiliations.


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