It’s not uncommon for medical marijuana critics to cite a “lack of research” as their main argument for not supporting the use of cannabis for medical purposes.
But as it turns out, there is no shortage of research into the medical benefits of cannabis. The volume of studies on the subject has boomed in recent years – from 3,000 total published papers in the 1990s to a staggering 30,000 in the past ten years alone.
With this vast pool of research to select from, it is increasingly evident that medical marijuana works as a treatment for countless medical conditions. Here, we’ve rounded up some of the most noteworthy peer-reviewed studies on the various ailments that medical marijuana is proven to treat. Keep reading to learn more!
A Shift in Medical Perspective
In 2013, Dr. Sanjay Gupta, a neurosurgeon and CNN’s chief medical correspondent, made waves with a public apology for opposing medical marijuana in the past:
I apologize because I didn’t look hard enough, until now. I didn’t look far enough. I didn’t review papers from smaller labs in other countries doing some remarkable research, and I was too dismissive of the loud chorus of legitimate patients whose symptoms improved on cannabis.
Gupta went on to address common misconceptions about marijuana’s federally illegal status:
I mistakenly believed the Drug Enforcement Agency listed marijuana as a schedule one substance because of sound scientific proof. Surely, they must have quality reasoning as to why marijuana is in the category of the most dangerous drugs that have “no accepted medicinal use and a high potential for abuse.
They didn’t have the science to support that claim, and I now know that when it comes to marijuana neither of those things are true. It doesn’t have a high potential for abuse, and there are very legitimate medical applications. In fact, sometimes marijuana is the only thing that works.
In 2015, Dr. Kate Scannell, formerly the medical director of one of the country’s first hospital AIDS wards, voiced a similar opinion:
From working with AIDS and cancer patients, I repeatedly saw how marijuana could ameliorate a patient’s debilitating fatigue, restore appetite, diminish pain, remedy nausea, cure vomiting, and curtail down-to-the-bone weight loss. The federal obsession with a political agenda that keeps marijuana out of the hands of sick and dying people is appalling and irrational.
Today, these opinions are far from unique in the medical field, with more doctors seeing the benefits of medical marijuana every day. While being just the tip of the iceberg of cannabis research, the following studies highlight a wealth of research that supports Gupta, Scannell, and the numerous medical professionals calling for a change in social perception.
JOURNAL: British Medical Journal (2021)
FINDING: Using mortality data from the CDC, U.S. census data, and data on storefront dispensary operations across 23 states, researchers analyzed mortality rates associated with all opioid types. They also looked at the association with medical and recreational marijuana dispensaries. They found that having two available marijuana dispensaries in a single country reduced opioid-related deaths by 17%. Having three dispensaries in the area further reduced deaths by 8.5%, indicating that more access to marijuana led to fewer opioid-related deaths.
JOURNAL: Pharmacology, Biochemistry, and Behavior (2020)
FINDING: After gathering and analyzing data from 51 studies where researchers administered cannabidiol (CBD) to humans and animals with a history of cocaine use, scientists found that CBD treatment reduced the occurrence of cocaine self-administration. They believe CBD works by interfering with chemical pathways in the brain connected to cocaine-induced reward stimulation and dopamine release.
JOURNAL: International Journal of Drug Policy (2020)
FINDING: Researchers analyzed data gathered by a survey of 2,102 people enrolled in Canada’s medical cannabis program. They found that after using medical cannabis, 44% of participants reported a decrease in alcohol use over 30 days, and 34% of participants decreased the number of standard drinks they had per week.
JOURNAL: World Federation of Neurology (2004)
FINDING: Scientists conducted a study involving the use of delta-9 tetrahydrocannabinol (THC) in ALS mouse models. The researchers found that treating the mice with THC at the onset of tremors slowed the disease process and increased the lifespan of mice with ALS. This study indicates that medical marijuana could be an even more effective treatment than the only FDA-approved drug for ALS (riluzole), which only extends lifespan by around two months compared to THC, which may extend lifespans by over three years.
Anxiety & PTSD
JOURNAL: Frontiers in Pharmacology (2016)
FINDING: Researchers reviewed studies on CBD regulation of fear memory processing – which can be responsible for triggering the fight or flight response at inappropriate times in patients with anxiety and panic disorders. The study also explored CBD’s effect on auditory fear memory by observing behaviors in rats with and without CBD in their system. In both cases, the researchers found that CBD helped decrease learned fear response, indicating that CBD could be an improvement for treating fear-based phobias and anxiety over traditional medications like antidepressants, which can have adverse side effects.
JOURNAL: Cannabis and Cannabinoid Research (2019)
FINDING: A study followed 146 medical cannabis patients who reported using benzodiazepines when they first began using cannabis to treat their anxiety. After completing a six-month course of cannabis therapy, 45.2% of patients no longer continued use of benzodiazepines such as Xanax and Valium. This finding indicates that medical cannabis can be an effective treatment for anxiety while allowing patients to discontinue benzodiazepine therapy.
JOURNAL: Journal of Psychoactive Drugs (2014)
FINDING: An analysis of data from 80 post-traumatic stress disorder (PTSD) patients applying to their state’s medical cannabis program sought to determine if there was an association between cannabis use and PTSD symptoms. Researchers found that study participants experienced more than a 75% reduction in PTSD symptoms when using cannabis compared to non-users.
JOURNAL: Frontiers of Neuroscience (2018)
FINDING: This retrospective review of medical cannabis research found that CBD can block disturbing memories while offering fewer side effects than traditional pharmaceutical medications. The results indicate that CBD may provide therapeutic benefits for disorders related to traumatic memories and inappropriate responses, such as PTSD.
JOURNAL: CNS Neuroscience & Therapeutics (2019)
FINDING: A clinical trial studied the effects of nabilone, a synthetic cannabinoid, on 47 patients with PTSD. Researchers found that 72% of the patients experienced a significant reduction in the intensity of nightmares or complete termination of nightmares altogether. Some patients also experienced improvement in quality of sleep, sleep time, night sweats, and daytime flashbacks.
JOURNAL: European Journal of Pharmacology (2009)
FINDING: Scientists experimented on rats to determine how exposure to stress affected cannabinoid CB1 receptor expression in the brain’s hippocampus. They found that chronic exposure to stress significantly reduced CB1 receptor binding in the dentate gyrus region of the hippocampus, which regulates anandamide – a brain lipid that plays a vital part in mood regulation. The findings indicate that chronic stress can restrict the production of anandamide, resulting in impaired fear extinction, chronic anxiety, and other symptoms of PTSD.
JOURNAL: Seminars in Immunology (2014)
FINDING: This review analyzed data from research papers regarding the association between CB1 cannabinoid receptors and stress. Researchers discovered that acute stress increases CB1 receptor signaling, which dampens the endocrine response. The authors also note that increased CB1 receptor signaling exacerbates stress and may contribute to the harmful effects of chronic stress.
JOURNAL: Frontiers of Molecular Neuroscience (2017)
FINDING: Researchers reviewed past studies involving cannabinoid signaling in relation to stress in the hippocampus and found that hippocampal endocannabinoid signaling contributes to emotional and behavioral flexibility during stressful situations. The findings indicate that impairing endocannabinoid signaling in the hippocampus after stressful events may contribute to the development of psychiatric disorders that involve chronic stress, such as PTSD.
JOURNAL: Nature Reviews Cancer (2003)
FINDING: This review focused on several studies concerning the effects of cannabinoids – like THC and CBD – on cancer cells. Researchers found that cannabinoids inhibited tumor growth in laboratory animals by modulating key cell-signaling pathways to induce tumor cell death. Notably, CBD did not harm non-cancerous cells.
JOURNAL: British Journal of Pharmacology (2005)
FINDING: In a laboratory setting, scientists evaluated the ability of CBD to impair tumor cell migration. They found the presence of CBD limited cancer cells’ ability to migrate, indicating that CBD may play a role in inhibiting tumor invasion in the body.
JOURNAL: Molecular Cancer Therapeutics (2011)
FINDING: This study used microscopy techniques to analyze breast cancer cells while exposed to CBD. Researchers found that CBD kills breast cancer cells by inhibiting cancer cell signaling and inducing stress to the endoplasmic reticulum of these cells.
JOURNAL: Journal of Molecular Medicine (2012)
FINDING: Researchers investigated the effects of CBD as a chemo-preventative (i.e., cancer preventing) agent in mice with colon cancer. CBD reduced lesions, polyps, and tumor formation in mouse test subjects. CBD’s reduction of cell proliferation indicates that CBD is an effective protector against cancer.
JOURNAL: Israel Medical Association Journal (2011)
FINDING: Researchers conducted retrospective interviews and examined disease activity, surgery needs, medications, and hospitalizations before and after cannabis use in 30 patients with Crohn’s disease. They found that 21 of the patients improved significantly after cannabis use, with a significant decrease in the need for surgery and medication for those who used cannabis.
JOURNAL: British Medical Journal (2012)
FINDING: Researchers gathered data from the National Health and Nutrition Examination Survey (NHNES) conducted by the Centers for Disease Control and Prevention (CDC), collecting and analyzing a total of 10,896 adults. They found that marijuana users had a lower prevalence of diabetes mellitus than non-marijuana users.
JOURNAL: The American Journal of Medicine (2013)
FINDING: After gathering data collected by the NHNES between 2005 and 2010, researchers analyzed the blood test results of 4,657 adults. They compared fasting insulin levels between self-reported marijuana users and non-users. They found that marijuana users had a lower fasting insulin level on average and appeared to have better carbohydrate metabolism than non-users. Marijuana users also seemed to have less insulin resistance.
JOURNAL: The New England Journal of Medicine (2018)
FINDING: In a randomized, placebo-controlled, double-blind study that spanned 30 clinical sites and included 225 people, researchers discovered that adding CBD to traditional seizure medicine significantly decreased the rate of drop (or atonic) seizures compared to the placebo group. Specifically, drop seizures decreased from baseline by 41.9% in the 20-mg CBD group and 37.2% in the 10-mg CBD group, compared to a 17.2% decrease in the placebo group.
JOURNAL: British Journal of Pharmacology (2012)
FINDING: Scientists conducted a study on mice and rats to assess the potential anticonvulsant effects of a cannabinoid called cannabidivarin (CBDV). They found that CBDV was an effective anticonvulsant and produced no adverse motor function side effects. These findings indicate that CBDV may be an effective standalone anti-epileptic drug, or could be a beneficial adjunctive treatment alongside traditional epilepsy drugs.
JOURNAL: Journal of Glaucoma ( 2010)
FINDING: In this position statement from the American Glaucoma Society, the society acknowledges that it has been widely shown that marijuana lowers intraocular pressure (IOP) in people with and without glaucoma. For this reason, the writers advise that marijuana can be a practical part of a treatment plan for glaucoma.
JOURNAL: Journal of Clinical Medicine (2020)
FINDING: This review of published research articles discusses the fact that there are many cannabinoid receptors in the retina where glaucoma disease processes can occur. The authors note that cannabinoid use effectively treats glaucoma due to the neuroprotective qualities of cannabinoid molecules that come from their interaction with the receptors in the retina.
JOURNAL: Journal of Acquired Immune Deficiency Syndrome (2004)
FINDING: Upon interviewing 252 HIV patients in public healthcare clinics, researchers found that marijuana was associated with the relief of common HIV/AIDS symptoms. This includes anxiety and depression relief in over half of the self-reported marijuana users. Improved appetite, decreased nausea, and increased happiness was also associated with self-administered cannabis. These findings indicate that cannabis may be an excellent anti-nausea drug to combat the adverse side effects of antiretroviral medications that can cause severe nausea and anorexia.
JOURNAL: Journal of Pain (2019)
FINDING: Researchers gathered data through Strainprint, a medical cannabis app that allows patients to track their symptoms before and after trying different doses and strains of cannabis. There were significant reductions in migraine and headache severity after cannabis use, and researchers found that inhaled cannabis can reduce migraine severity by up to 50%.
JOURNAL: Pharmacotherapy (2016)
FINDING: This retrospective chart review analyzed data from 121 adults who had been recommended marijuana to treat migraines by a physician. The study found that patients who used marijuana experienced an average of 5.8 fewer migraine days per month. Notably, patients reported that using marijuana successfully stopped in-progress migraines.
JOURNAL: European Medical Journal (2017)
FINDING: This study presented at the Third Congress of the European Academy of Neurology investigated the use of cannabinoids in chronic migraine patients. Scientists gave patients varying daily doses of CBD and THC over three months. They found that both CBD and THC effectively reduced pain from migraines by 43.5%.
JOURNAL: Neurology (2005)
FINDING: A double-blind, placebo-controlled study that spanned five weeks was performed on multiple sclerosis patients who used whole-plant cannabis-based medications (such as THC and CBD) to treat their symptoms. Researchers found that cannabinoids effectively reduce sleep disturbances and pain in multiple sclerosis patients with central neuropathic pain.
JOURNAL: American Journal of Epidemiology (2011)
FINDING: Researchers reviewed two population-based and nationally represented studies that explored the relationship between the use of marijuana and obesity. They analyzed data from over 50,000 survey respondents. They found that cannabis users had a significantly lower prevalence of obesity than non-users, with the number of obese participants decreasing as cannabis use frequency increased. These findings indicate that despite evidence that cannabis stimulates appetite, cannabis users are less likely to be obese than non-users.
JOURNAL: The American Journal of Cardiology (2006)
FINDING: This retrospective study analyzed 15 years of data gathered by the Coronary Artery Risk Development in Young Adults (CARDIA) study. Researchers sought to determine how marijuana use was associated with caloric intake, body mass index (BMI), and cardiovascular risk factors. Although marijuana use may be correlated with increased caloric intake and alcohol use, it is not associated with higher glucose levels or BMI.
JOURNAL: Medical Society of Delaware (2021)
FINDING: This 18-month study looked at the effect of adding medical marijuana to existing pain management treatment plans that included opioids. Researchers found that patients who used medical marijuana reported a 31% decrease in opioid use. Specifically, they found that:
- The reduction in opioid use for patients with neck pain was 41%.
- Patients with low back pain reported a 29% decrease in opioid use.
- Patients with knee pain decreased their opioid intake by 32%.
JOURNAL: Cureus (2020)
FINDING: Researchers conducted a survey on patients from three medical cannabis clinics who had reported using opioids to manage chronic pain. After analyzing data from 525 patients, they found that cannabis use was an effective adjuvant to opioids and, in some cases, could entirely replace the need for opioids. Specifically, the study found that when marijuana was used to treat chronic pain:
- 40% of responders reported that they stopped using all opioids.
- 45% reported some decrease in opioid use.
- 48.5% reported a decrease in pain by 40% or over.
- 62% of responders did not want to take opioids in the future.
- 87% reported improved quality of life.
JOURNAL: Journal of Pain ( 2008)
FINDING: This double-blind, placebo-controlled, crossover study evaluated the effect of inhaled cannabis on neuropathic pain. After administering standardized doses of cannabis to 38 patients with peripheral and central neuropathic pain, scientists found that cannabis equally reduces pain intensity and unpleasantness. This discovery indicates that, like opioids, cannabis does not rely on sedation to relieve pain. It equally reduces both the emotional and physical components of the pain experience.
JOURNAL: Clinical Neuropharmacology (2014)
FINDING: Scientists observed 30 Parkinson’s patients before and after smoking marijuana to assess the effects of cannabis on Parkinson’s disease motor symptoms. They found that marijuana use significantly improved Parkinson’s-related tremors, rigidity, and bradykinesia. There was also a significant improvement in sleep and pain scores.
JOURNAL: Evidence-based Complementary and Alternative Medicine (2015)
FINDING: After analyzing data gathered from self-administered surveys completed by 207 Parkinson’s patients in the Denver metro area, researchers found that cannabis was effective at improving sleep and mood more than any other complementary or alternative medications.
JOURNAL: Journal of Psychopharmacology (2014)
FINDING: This study on 21 Parkinson’s patients explored the effect of CBD on Parkinson’s symptoms. Researchers found that high doses of daily CBD were associated with increased functioning and well-being compared to the placebo group.
Respiratory Health: Risk Rebuttals
JOURNAL: Journal of the American Medical Association (2012)
FINDING: This study followed 5,115 people over 20 years to investigate the relationship between marijuana use and pulmonary function. The results found that occasional and low cumulative marijuana use was not associated with negative effects on pulmonary function.
JOURNAL: Respiratory Care (2016)
FINDING: After conducting a systematic review of research involving the effects of inhaling marijuana, the authors warned that little is currently known about the impact of marijuana smoke compared to the wealth of information known about tobacco smoke. For this reason, inferences cannot be made about one type of smoke inhalation based on the other.
JOURNAL: Cancer Causes & Control (1997)
FINDING: This retrospective cohort study examined the relationship between cancer and marijuana use. After analyzing data from 64,855 participants, the authors found that marijuana use was not associated with tobacco-related cancers, melanoma, or lung, breast, and colorectal cancers.
JOURNAL: Cancer Epidemiology, Biomarkers, & Prevention (2006)
FINDING: Scientists conducted interviews with 611 lung cancer patients to evaluate the connection between cannabis smoking and lung cancers. The results revealed that chronic low cannabis exposure was not linked to an increased risk of lung cancer or other upper aerodigestive tract cancers.
JOURNAL: Archives of Internal Medicine (2006)
FINDING: This systematic review of 19 studies assessed the impact of smoking marijuana on lung cancer. The authors discovered that there was no statistical significance linking cannabis inhalation and lung cancer.
Nearly 70% Of Clinicians Agree: Cannabis Has Medical Use
As the volume of promising research grows, so does the number of healthcare providers who see the value of cannabis as a valid medical treatment. A 2021 survey of family practice doctors, oncologists, nurse practitioners, and internists found that nearly 70% of respondents agreed that cannabis has medical uses.
While the increased acceptance of medical marijuana shown in this study is promising, the number of respondents who had prescribed medical marijuana to their patients was low, even for clinicians who agreed that cannabis has medical use. Even more concerning is that 60% of respondents could not correctly answer questions about marijuana’s legal status in their own state.
This lack of understanding is most likely why so many clinicians are reluctant to prescribe medical marijuana to their patients. To solve the issue, healthcare providers must educate themselves on the benefits of marijuana and the relevant laws in their state. Only then can they make informed decisions about marijuana that can benefit their patients.