Why You Need to Talk About Cannabis With Patients

A few years ago, UCLA Health began asking patients if they used cannabis as part of an electronic previsit questionnaire completed before well visits. The question is still an unusual ask for most primary care clinicians, said Lillian Gelberg, MD, a professor of family medicine at the UCLA David Geffen School of Medicine.

“Doctors don’t ask, and patients don’t tell,” she said. 

If a patient’s answers indicate a risk for cannabis use disorder— a complex diagnosis that involves clinically significant impairment or distress linked to the drug over a 12-month period — Gelberg receives a flag before the visit, enabling her to provide a brief intervention.

“What I say to them is, ‘I thank you for completing your questionnaire, and I’m concerned about your scores on your cannabis screen,’” Gelberg said.

The rate of people older than 12 years in the United States reporting daily or near-daily use of cannabis rose 15-fold between 1992 and 2022 , with an increase in absolute numbers of daily or near-daily users from about 1 million to 17.7 million over that period.

And while some clinicians may not think their patients are part of that increase, screening may help identify those who are. A study of nearly 1700 patients found that 38.8% responding to a confidential survey in 2021 reported using cannabis in the previous year, but only 4.8% had that information in their electronic health record.

Meanwhile, average levels of tetrahydrocannabinol (THC) in cannabis samples in the United States rose from 3.96% in 1995 to 16.14% in 2022. The drastic increases in potency, combined with inconsistent regulations between states, such as caps on potency or tracking systems verifying product quality, should be of concern, according to Fred Rottnek, MD, a professor and director of community medicine, as well as the program director of the addiction medicine fellowship , at the Saint Louis University School of Medicine in St. Louis.

Experts say primary care clinicians need to ask about cannabis use to better counsel their patients about the health risks of the substance. A recent study published in JAMA Network Open reported a nearly threefold risk for death in patients within 5 years following an emergency department visit or a hospitalization due to cannabis use disorder. The causes of death linked to cannabis use included suicide, trauma, poisonings linked to opioids and other drugs, and lung cancer.

And complications of cannabis can happen to anyone: Emergency department visits in adults older than 65 years were 19 times higher in 2019 than in 2005 in California.

Why Ask?

Researchers at UCLA Health identified actionable items — such as the identification of cannabis use disorder, need to discuss interactions with common prescription medications, and safety issues associated with the presence of edibles in the home— after they began screening sent out through their electronic health record in 2021.

Overall, 17% of patients reported using cannabis, and 34.7% of those patients had results indicating a moderate to high risk for cannabis use disorder.

Marjan Javanbakht, PhD, an adjunct professor in the Department of Epidemiology at the UCLA Fielding School of Public Health and co-lead author of the study, said her team uncovered much more cannabis use than they expected. She was also surprised at the 80% of patients who classified themselves as recreational users who were taking cannabis to manage a symptom. The most common uses were for sleep (56%), mental health symptoms (55.5%), stress (50.2%), worry or anxiety (36.3%), and nonspecific pain (31.7%).

“Patients may be using marijuana instead of the medications that we’re prescribing for them,” Gelberg said. “And we need to have a dialogue about that.”

Talking with adults older than 65 years is also crucial because this population prefers consuming cannabis through edibles, Rottnek said.

“Edibles don’t kick in as quickly because like most drugs taken orally, it takes a while for them to absorb,” Rottnek said. Intoxication increases fall risks in older adults. In addition, clinicians may want to counsel patients on safe storage of their cannabis products if grandchildren or other children are in the home. Unintentional intoxication from edibles is well-documented in children: Between 2017 and 2021, 22% of such episodes in children reported to US poison control centers resulted in hospitalization. 

Clinicians may also want to talk to patients about interactions between cannabis and other medications, such as commonly prescribed analgesic, psychotropic, and cardiovascular agents. Both THC and cannabidiol (CBD) can alter levels of certain opioids, statins, antidepressants, and anticoagulants. THC also can increase the effects of central nervous system depressants, such as alcohol and benzodiazepines, increasing the risk for memory loss and confusion in older adults.

For his younger patients, Rottnek said he worries about those with a family history of schizophrenia.

“A lot of young people, teenagers and young adults, are showing up in ERs [emergency rooms] for psychotic breaks that can go for 5-7 days, depending on the potency of what they’re using,” he said.

He also noted the risks associated with cannabis use during pregnancy, such as low birthweight in infants and psychopathology later in childhood.

How to Ask

When Rottnek teaches medical students, residents, and fellows about clinical interviewing, he advises starting with legal substances: Alcohol, tobacco, and cannabis. He advised against using the phrase, “You don’t smoke or drink, do you?” Instead, clinicians should adopt a more open-ended approach, such as, “Tell me about your cannabis use.”

If a patient says they do use various substances, he asks about the route of ingestion, frequency of use, and why they use the substance to inform his discussion of how to reduce potential harms.

The researchers from UCLA used a more systematic approach, using the World Health Organization’s screening test adapted for tobacco and cannabis. Javanbakht said patients are more truthful on self-administered, computerized questionnaires, which also save time for the clinician.

Take Home Messages for Your Patients

Many clinicians might associate harm reduction with syringe access or safe injection practices, but Rottnek said harm reduction is about making good day-to-day decisions.

“If somebody’s engaging in an inherently risky behavior, how do you mitigate bad things from happening?” he said.

He bases his harm reduction approach to counseling on a systematic review of measures to lower health risks for anyone using cannabis. Clinicians should advise patients to:

• Choose low-potency THC or balanced cannabis products with a balanced ratio of THC to CBD because products high in THC are associated with higher risks for acute and chronic mental health and behavioral problems.
• Limit use to 1 d/wk or weekends only. Daily use has been linked to mental health problems, cardiovascular disease, motor vehicle accidents, suicidal behavior, and neurocognitive effects.
• Abstain from using synthetic cannabinoids because more severe health effects have been linked to these products.
• Avoid combusted cannabis inhalation and instead use nonsmoking use methods. Regular inhalation of cannabis can induce chronic bronchitis.
• Avoid deep inhalation or breath holding to increase absorption, which can damage the lungs.
• Do not drive or operate heavy machinery for 6 hours after using cannabis.
• People with a history of schizophrenia, uncontrolled hypertension or coronary artery disease, or chronic obstructive lung disease or other lung pathology should not use cannabis because of a higher risk for related health problems.

Gellberg, Javanbakht, and Rottnek reported no financial conflicts of interest. 

A former pediatrician and disease detective, Ann Thomas is a freelance science writer living in Portland, Oregon.