In 1996, California became the first state to legalize medical marijuana. Today, the use of cannabis to treat health conditions is now legal in 38 states, three territories and Washington, DC.
As legalization has spread across the United States, the percentage of people who report having a medical clearance to use cannabis has doubled in the last decade, rising from 1.2% to 2.5% between 2013 and 2020.
But Thomas Arkell, PhD, a postdoctoral researcher at Swinburne University of Technology in Melbourne, Australia, says clinical trials of the effectiveness of the medical marijuana active ingredients THC and CBD are still in their infancy.
We need to build a stronger evidence base on what kinds of doses of THC and CBD are most effective for certain conditions, which delivery forms work best, and what are the reasons why some patients discontinue treatment due to lack of symptom improvement says Dr. Arkell, co-author of a new study on cannabis use and health-related quality of life, published May 9, 2023, in JAMA network open.
Perhaps the largest study of its kind, according to Arkell, the study found that medical cannabis led to significant improvements in a number of measures of quality of life, including both physical and emotional health.
2 out of 3 participants use medical cannabis for chronic pain
For the study, the researchers analyzed data from 3,148 patients. About 54 percent were women and 30 percent were employed, with an average age of 56.
Approximately two-thirds of subjects used cannabis to treat chronic non-cancer pain, followed by cancer pain (6%), insomnia (5%) and anxiety (4.2%).
The study used a standardized questionnaire frequently used in research to measure health-related quality of life in people with chronic health conditions, as described in past research. Includes questions about general health, activity limitations, physical health issues, emotional health issues, pain, energy, emotions, and social activities. The test consists of scaled scores in 8 different domains, with each scale translated into a score between 0 and 100. The lower the score, the greater the disability.
The study suggests real improvement with medical cannabis use, says one of its co-authors
After initiating medical cannabis treatment, patients reported significant improvements from baseline in all eight domains of the questionnaire, and for the most part, those improvements were maintained, according to the authors.
After controlling for potential confounders, including the number of other medications the person was taking, the number of comorbid illnesses reported, age, gender, and occupational status treatment with medical cannabis was associated with an improvement of approximately 6- 18 points, depending on the domain.
Prescribed use of medical cannabis appears to be associated with long-term gains in a number of different health-related quality-of-life measures. This suggests real improvement in physical and mental health and daily function, which is critical for patients with chronic disease, Arkell says.
Access to medical marijuana varies between Australia and the United States
Most cannabis prescriptions were for orally administered products, including oils and capsules.
It’s important to note that there are large differences in how medical cannabis is obtained by patients in Australia versus the United States, Arkell says.
In Australia, the model is like getting a prescription drug filled in the US, where doctors prescribe a specific dose and product which is picked up at the pharmacy. In the United States, people must qualify for a medical marijuana card to use at a dispensary to buy whatever they want with their medical cannabis license, she explains.
This means that the doctor in Australia has much more control over the type of product, THC dose and frequency of use, which can translate into better clinical outcomes, he says.
Medical marijuana can have unwanted side effects
A total of 2,919 adverse (undesirable) events were reported during the study, and 86 were serious, including 2 considered serious.
Adverse events were common, which means we need to be aware of the risks of prescribing THC and possible side effects. These risks need to be weighed in the context of what other drugs a patient is already using and can dictate what maximum THC a patient should use, Arkell says. Most of the adverse events were common, fleeting side effects of THC (the component of marijuana that leads to a high), and very few were serious, she added.
The study design may exaggerate the benefits of medical marijuana
The design of this study is flawed in two ways, says Keith Humphreys, PhD, a professor of psychiatry and behavioral sciences at Stanford University in Palo Alto, California, who was not involved in the research.
The first way is that the study excluded all people who started the product and then didn’t come back. Even in their most successful follow-up, fewer than half of the people returned, Dr. Humphreys points out.
That means a large proportion of people withdrew from the study by not returning, and there has been no follow-up with these participants, she says.
This can give the illusion of, Wow, these people have really improved. But for a study of any treatment, if you eliminate all the people who didn’t respond or who had a positive experience, that data can look really good, she says.
The other problem with this study is one the authors acknowledge: There is no placebo control, Humphreys says. So we see people using the product and the subset left in the study say they felt better, but they could have felt better if we had given them a sugar pill. There’s no way to tell because there wasn’t a comparison group, he says.
There really isn’t much good evidence that medical marijuana improves health-related quality of life, and because of the flaws in this study, it doesn’t add any new information, says Humphreys.
Several authors revealed financial ties to the pharmaceutical and cannabis industry, and the data collection and study was funded by a for-profit company that sells medical cannabis products.
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