Mixed Findings on Effectiveness of Medical Cannabis
/By Pat Anson
Some new studies are muddying the water even more on whether medical cannabis is an effective treatment for pain, anxiety, insomnia and other health conditions.
The first study, a review of over 120 clinical trials, medical guidelines and meta-analyses (a study of studies) published in JAMA, found that there is not enough scientific evidence to support most of the conditions that cannabis is commonly used to treat.
Over one in four (27%) adults in the United State and Canada have used cannabis for medical purposes. And over 10% of people in the U.S. have used products containing cannabidiol (CBD) for therapeutic purposes.
But researchers say that widespread use is driven more by perceptions, anecdotes and promotion than it is by scientific evidence.
"While many people turn to cannabis seeking relief, our review highlights significant gaps between public perception and scientific evidence regarding its effectiveness for most medical conditions," says lead author Michael Hsu, MD, a psychiatrist and health researcher at UCLA Health.
“Patients deserve honest conversations about what the science does and doesn't tell us about medical cannabis.”
Hsu and his colleagues found that FDA-approved cannabis-based medications, such as dronabinol and nabilone, are effective for conditions such as HIV/AIDS-related appetite loss, chemotherapy-induced nausea, and pediatric seizure disorders such as Dravet syndrome and Lennox-Gastaut syndrome.
But for most other conditions, the evidence remains either inconclusive or lacking. Over half of medical cannabis users take it for chronic pain, but current medical guidelines recommend against cannabis as a first-line treatment for either chronic or short-term acute pain.
The researchers also highlighted the potential health risks of cannabis. High-potency cannabis containing over 10% THC has been linked to higher rates of psychotic symptoms and anxiety disorder.
Daily use of cannabis, particularly of inhaled or high-potency products, is also associated with higher rates of coronary heart disease, heart attack and stroke compared to non-daily use.
About 29% of people who use medical cannabis also met the criteria for cannabis use disorder.
The review emphasizes that doctors should screen patients for cardiovascular disease and psychotic disorders, and evaluate for potential drug interactions, before recommending THC-containing products for medical purposes.
Medical Cannabis Reduces Opioid Use
But another study, published in JAMA Internal Medicine, suggests that medical cannabis is an effective treatment for chronic pain because it reduces the use of prescription opioids.
Researchers at Albert Einstein College of Medicine and Montefiore Health System evaluated 204 adults in New York State’s Medical Cannabis Program who were prescribed opioids for chronic pain between 2018 and 2023.
At the start of the 18-month study, most participants reported high levels of pain and were taking an average daily dose of 73.3 morphine milligram equivalents (MME). By the end of the study, the average daily dose fell to 57 MME, a 22% reduction.
“Our findings indicate that medical cannabis, when dispensed through a pharmacist-supervised system, can relieve chronic pain while also meaningfully reducing patients’ reliance on prescription opioids,” said lead author Deepika Slawek, MD, an associate professor of medicine at Einstein, and an internal medicine and addiction medicine specialist at Montefiore.
The reduced use of opioids suggests that chronic pain sufferers can be slowly weaned off opioids by using medical cannabis. For example, participants who received a 30-day supply of medical cannabis reduced their opioid use by an average of 3.5 MME per day compared to non-users.
“Those changes may seem small, but gradual reductions in opioid use are safer and more sustainable for people managing chronic pain than stopping suddenly,” said Slawek.
Since the study occurred during a time period when opioid prescribing overall fell by nearly 50% in the United States, we asked Dr. Slawek if that could have influenced the findings. She said researchers adjusted their modeling data to account for that as best they could.
“The only way that we will be able to get definitive answers on whether medical cannabis reduces opioid use is to conduct randomized trials, which are very difficult to do in the U.S. specific to cannabis,” Slawek told PNN in an email.
“We believe that by using causal inference modeling in this study, we were able to add the highest quality evidence possible (without conducting a randomized trial) that cannabis may reduce opioid use in patients with chronic pain.”
The scientific data for medical cannabis is improving. According to an analysis by the National Organization for the Reform of Marijuana Laws (NORML), cannabis research studies grew for the fifth consecutive year, with over 4,000 scientific papers involving cannabis published so far in 2025.
“Despite the perception that marijuana has yet to be subject to adequate scientific scrutiny, scientists’ interest in studying cannabis has increased exponentially in the past decade, as has our understanding of the plant, its active constituents, their mechanisms of action, and their effects on both the user and upon society,” said NORML Deputy Director Paul Armentano.
“It is time for politicians and others to stop assessing cannabis through the lens of ‘what we don’t know’ and instead start engaging in evidence-based discussions about marijuana and marijuana reform policies that are indicative of all that we do know.”
According to NORML’s analysis, over 37,000 scientific papers about cannabis have been published since 2015. That means over 70% percent of all peer-reviewed scientific papers about cannabis have been published in the past ten years alone.
The studies are growing and so is the anecdotal evidence. A recent survey of 1,669 medical cannabis users in the UK found that nearly 89% of those with chronic pain reported somewhat improved or significantly improved quality of life.
