Pharmacists Facilitate Harm Reduction for Patients With Anxiety Using Cannabis


Data for generalized anxiety disorders and cannabis use is scarce, but pharmacists can help educate patients on potential benefits and risks of cannabis usage.

The main role for pharmacists in cannabis use is harm reduction, said Tiffany R. Buckley, PharmD, BCPS, BCPP, advanced practice psychiatric pharmacist at the University of Maryland School of Pharmacy, in a session at the American Association of Psychiatric Pharmacists Conference 2024.

“Anxiety disorders are very, very common,” Buckley said in the session. “Anxiety is actually the most common reason, besides chronic pain, that people actually purse treatment with medical cannabis.”

marijuana cannabis leaf background

Image credit: YARphotography |

Cannabis is a schedule 1 controlled substance, although various states allow for medical or adult use of the drug, Buckley said. The most commonly studied phytocannabinoids are tetrahydrocannabinol (THC) and cannabinoid (CBD). Buckley added that cannabis affects the endocannabinoid system, which in turn impacts the nervous and endocrine systems. For patients with anxiety, impacts on the endocannabinoid system can lead to disruptions in nervous and endocrine systems, causing the systems to be dysregulated. The endocannabinoid system can stop neurotransmission and does play an important role in mental health.

Currently, there is no classification system for cannabis, but scientifically, professionals are working on classifying it. For now, Buckley said, they use chemotypes. For example, chemotype I would be predominantly THC cannabis, chemotype II would be a balance of THC and CBD, and chemotype III would be predominantly CBD. She recommended chemotype III for patients that want to use cannabis, but emphasized that pharmacists’ roles should be dose management and harm reduction because there is not a lot of evidence for cannabis in individuals with anxiety disorders.

THC is a partial agonist of CB1, according to Buckley, which could help change neurotransmission and balance it. In low doses, THC can help reduce anxiety, but in higher doses, it can completely block the endocannabinoid system from working. CBD’s mechanism of action remains unclear, though in small studies it has been shown to reduce blood flow to areas in the brain that are active for those with anxiety.

“The data is not very good, but we can recommend different harm reduction strategies. It's important to really think about the patient that's in front of you, the risk and benefits of cannabis therapy, and then educate them on why those things are important to consider,” Buckley said in the session.

Typically, studies of both CBD and THC have been conducted with individuals who are healthy or who have social anxiety disorders (SAD). According to one study Buckley presented, when THC was increased in healthy patients or those with SAD, anxiety also increased. For CBD, there were reports of decreased anxiety with minimal adverse effects. In a large longitudinal study, medical cannabis reduced anxiety in individuals, with the largest decreases occurring after 1 to 3 months. Buckley added that even with these studies, there is a small pool of data for anxiety, and no data for generalized anxiety disorder.

Pharmacists play an important role in harm reduction, Buckley added. She said that it is essential to collect information to best treat and educate patients.

“As a pharmacist, what we want to do when these patients come in is, first, we just want to try to optimize their profile. Have they tried everything [else] first? And then we can talk about cannabis, but we want to convey to them that we do still want to talk about cannabis because they want to talk about it,” Buckley said in the session.

She emphasized that asking more questions about cannabis use is essential. Such questions can include what type of cannabis they use, what the dose is, how frequently is the patient using, where are they getting the cannabis from, and how are they consuming it.

She also reminded attendees that every patient is different, and every experience is different, even for the same patient. Every time they consume cannabis, they can have a different experience, so it is important to educate patients on that, as well. Further, she said that patients with anxiety who tend to use cannabis more frequently should be screened for cannabis use disorder.

Age is one notable variable to consider. Buckley said that patients aged 65 and older are more susceptible to THC, even in low doses, and patients aged less than 25 still have developing brains, so higher levels of THC can increase chances of psychosis, addiction, suicide, memory, cognitive impairment, and executive function difficulties.

She added that other health conditions can affect cannabis effects, such as respiratory and cardiovascular diseases, which can become worse when inhaling cannabis. Cannabis with severe kidney disease is generally safe, but contamination with heavy metals, pesticides, and solvents could be problematic. Severe liver disease could also make patients more sensitive to the effects of cannabis. Mental health changes should be recorded and monitored, and individuals with a family history of psychosis should not use THC, Buckley said. Individuals who have substance use disorder are also at higher risk of addiction.

Further, for those who are pregnant or breastfeeding, there is little data on how cannabis use could affect the infant or developing embryo. Buckley added that it is essential to have a list of all the patient’s medications, as well, but many drug-drug interactions with cannabis are still unknown.

To minimize harm, Buckley recommends CBD-predominant cannabis, or strains with lower levels of THC, but said they should be used with caution. Additionally, dosage form is dependent on the patient because each patient is different and some might need faster onset. However, she cautioned against chemically concentrated extracts. Furthermore, there are no recommended guidelines for dosage, but she suggested to start low, then increase if needed.

Furthermore, Buckley said that initially, providers should follow up every 2 to 4 weeks, but if there is no progress after 3 months, discontinue cannabis.

“We don't know what's going to work with someone; all we can do is just take the basics and the evidence and extrapolate. We really need people to report what they're using, so we can help them and see whether it's actually working,” Buckley said in the session.


Buckley TR. Not So Positive: Treating the Negative and Cognitive Symptoms of Schizophrenia. American Association of Psychiatric Pharmacists Conference 2024; Orlando, Florida; April 7-10, 2024.

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