--- title: Medical Marijuana: Here's What Science Says About Whether it Works description: It’s buyer-beware for medical marijuana users, since the data supporting the benefits of cannabinoids are still in flux, and most marijuana edibles aren’t well labeled canonical: https://time.com/3931863/medical-marijuana-benefits/ author: Alice Park article:opinion: false article:content_tier: free article:published_time: 2015-06-23T15:15:05.000Z article:modified_time: 2026-05-11T05:02:52.871Z article:section: Health og:title: Here's What Science Says About Medical Marijuana og:description: It’s buyer-beware for medical marijuana users, since the data supporting the benefits of cannabinoids are still in flux, and most marijuana edibles aren’t well labeled og:url: https://time.com/3931863/medical-marijuana-benefits/ og:site_name: TIME og:image: https://static.time.com/v3/assets/bltea6093859af6183b/blta09e0bbc53daa690/6987ee135f570fd910b196c7/marijuana-leaf.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 og:image:width: 4264 og:image:height: 2399 og:image:alt: Marijuana leaf on a white background og:type: article twitter:card: summary_large_image twitter:title: Here's What Science Says About Medical Marijuana twitter:description: It’s buyer-beware for medical marijuana users, since the data supporting the benefits of cannabinoids are still in flux, and most marijuana edibles aren’t well labeled twitter:image: https://static.time.com/v3/assets/bltea6093859af6183b/blta09e0bbc53daa690/6987ee135f570fd910b196c7/marijuana-leaf.jpg?branch=production&width=1200&quality=75&auto=webp&crop=16:9 ---  # Here's What Science Says About Medical Marijuana > Sponsored content. 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Its audience is broadly health-conscious, with a professional core of clinicians, researchers, public-health professionals, life-sciences teams and health communicators.  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Jun 23, 2015 3:15 PM UTC  Marijuana leaf on a white background Marijuana leaf on a white backgroundGetty Images  by [Alice Park](https://time.com/author/alice-park/)  ## Alice Park Senior Correspondent Jun 23, 2015 3:15 PM UTC There’s a big difference between anecdotal evidence and scientific proof, and the field of medical marijuana research is filled with more of the former than the latter—in part because marijuana is [notoriously difficult to study](http://time.com/3858353/the-great-pot-experiment/) because it’s classified as a schedule-1 drug. Scientists led by Penny Whiting from University Hospitals Bristol in the U.K. [report in _JAMA_](http://jama.jamanetwork.com/article.aspx?doi=10.1001/jama.2015.6358) that there is only moderate-quality evidence supporting the benefits of medical marijuana, and only for certain conditions. The majority of studies involving medical marijuana are of lesser quality and therefore more likely to be biased and provide unreliable results. **MORE:** [Teens Don’t Smoke More Pot After Medical Marijuana Laws Passed, Study Finds](http://time.com/3922534/legalized-marijuana-teens-study/) In all, Whiting and her colleagues analyzed 79 randomized trials, the gold standard in medical research in which volunteers are randomly assigned to take a cannabis-related product or a placebo. The studies evaluated marijuana’s ability to relieve a range of symptoms including nausea from chemotherapy, loss of appetite among HIV positive patients, multiple sclerosis spasms, depression, anxiety, sleep disorders, psychosis and Tourette syndrome. Most of the studies showed improvements among the participants taking the cannabinoid products over those using placebo, but in many, the scientists admitted that they could not be sure that the effect wasn’t simply due to chance since the association was not statistically significant. **MORE:** [The Great Pot Experiment](http://time.com/3858353/the-great-pot-experiment/) The strongest trials supported cannabinoids’ ability to relieve chronic pain, while the least reliable evidence involved things like nausea and vomiting from chemotherapy, sleep disturbances and Tourette syndrome. Cannabinoids were, however, connected to more adverse events such as nausea, vomiting, dizziness, disorientation and hallucinations than placebo. Summing up the state of the evidence, Whiting and her colleagues write that “Further large, robust, randomized clinical trials are needed to confirm the effects of cannabinoids, particularly on weight gain in patients with HIV-AIDS, depression, sleep disorders, anxiety disorders, psychosis, glaucoma, and Tourette syndrome.” ### Go Inside the Harvest of Colorado's Most Controversial Marijuana Strain  Charlotte's Web grows on the Stanley brother's farm near Wray, Colo. on Sept. 22, 2014\. The Stanley Brothers have developed a popular strain of cannabis that has been found to be helpful in reducing seizures in some children. Charlotte's Web is high in a compound called cannabidiol (CBD) and low in tetrahydrocannabinol (THC) the compound that causes a high. Matt Nager for TIME  Charlotte's Web grows on the Stanley brother's farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  From left: Zachary Sobol, Michael Atchley, and Jared Stanley walk to the farm to prepare for harvest of Charlotte's Web near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Rows of Charlotte's Web await harvest at the Stanley brother's farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Jared Stanley helps in the harvest of Charlotte's Web on the Stanley brother's farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Colin Sparks searches for seeds during the harvest of Charlotte's Web on the Stanley brother's Charlotte's Web farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Discarded leaves of Charlotte's Web at a farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Tim Knight helps in the harvest of Charlotte's Web on the Stanley brother's farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Rows of Charlotte's Web await travel to a drying facility after being harvested on a farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Zachary Sobol catches a ride on a trailer to the Stanley brother's farm during harvest of Charlotte's Web near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Rows of Charlotte's Web await travel to a drying facility after being harvested from a farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  One of the Stanley brother's greenhouses growing cannabis near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Zachary Sobol hangs rows of Charlotte's Web to dry after harvest in Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  Penn Mattison, left, and Zachary Sobol, right, hang rows of Charlotte's Web to dry after being harvested from a farm near Wray, Colo. on Sept. 22, 2014. Matt Nager for TIME  The Stanley brothers' new company laboratory in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME  A petri dish full of cannabis explants await transfer and transplanting at the Stanley brothers' lab in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME  Molecular plant biologist and lab manager Bear Reel awaits the cooling of agar to help induce rooting of transplanted cannabis plants at the Stanley brothers' company laboratory in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME  The lab notebook of molecular plant biologist and lab manager Bear Reel at the Stanley brothers' company laboratory in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME  A flask of agar cools before explants of hemp are transplanted to help induce rooting and new growth at the Stanley brothers' company laboratory in in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME  Tissue cutter technician Meg Regan holds a vial of explants before sanitizing and transplanting at the Stanley brothers' laboratory in Boulder, Colo. on Sept. 23, 2014. Matt Nager for TIME **MORE:** [Even in Colorado Medical Marijuana Can Still Get You Fired](http://time.com/3921738/coats-colorado-dish-medical-marijuana-work-law/) That puts patients who try medical marijuana products at a crossroads — in 23 states and Washington, DC, laws allow doctors to recommend cannabis products for their patients for medical reasons. But with little in the way of solid scientific evidence for which products works best, and in which doses, it’s up to the patients to adopt trial-and-error to figure out which, if any cannabinoids help to relieve their symptoms. Adding to the confusion for patients, [another study published in the same _JAMA_ issue](http://www.elabs10.com/c.html?ufl=c&rtr=on&s=x8pbgr,29n8i,2kek,43ig,g2u3,hb35,8zrx) shows that medicinal marijuana food products, which include things such as candies, brownies and teas, aren’t often labeled correctly when it comes to their most active cannabis ingredient, and that the amounts are inconsistent. Ryan Vandrey, associate professor of psychiatry and behavioral sciences at Johns Hopkins University School of Medicine and his colleagues evaluated the contents of 75 products from 47 different brands purchased at marijuana dispensaries in San Francisco, Los Angeles and Seattle, where medicinal marijuana use is legal. When they analyzed them for their content of THC and cannabinoids, the two most concentrated chemicals found in marijuana, they found wildly divergent amounts from what was noted on the products’ labels. Among them, only 17% were accurately labeled, with 23% of the products containing more of these compounds than listed, and 60% containing less than advertised. The labels noted that anywhere from 2 mg to 1000 mg of these agents were in the products, while the lab-based analysis revealed readings as low as 1mg to as high as 1237 mg. “When I have a health condition, and need to go buy my medicine, I want to make sure I know what I’m getting,” says Vandrey. “I want to make sure the dose I buy is the same today and the same the next time and the same the next time I buy it. I want reliability and accuracy so I don’t end up with problems.” **MORE:** [How Much Does Marijuana Impact Your Driving?](http://time.com/3930541/marijuana-impact-driving/) But medical marijuana products, he says, aren’t regulated by the same system that vets other pharmaceutical drugs. In fact, cannabinoids are not regulated at all, since the federal government still considers marijuana an illegal substance and therefore does not acknowledge that marijuana-based therapies exist at all. So far, 23 states have legislated such medicinal marijuana into legality, which means that legislation, and not scientific criteria, have “approved” these compounds for medical use. The results? “What we saw was that there cant’ be much if any consumer confidence within the cities we purchased and tested products,” says Vandrey. For the larger medical marijuana distributors who see the emerging market as a profitable business, there’s the concern that profit motives may push them to under-deliver the amount of THC or cannabinoid they note on the label. And for the smaller outfits, it could be a matter of not knowing how to extract and measure the active ingredients from the cannabis plant and distribute it in a consistent way in a batch of tea or baked goods. How can consumers know what they’re getting in a medical marijuana edible? They can do their homework and talk to other consumers and the dispensary about dosing of THC and cannabinoids, says Vandrey. Or they can try to test the products themselves, which some states offer in an effort to standardize and gain more control over these products. But ultimately, he says. “if states are going to supersede federal law and say we think there is medical benefit in marijuana, and we want it to be available to our residents, then it should also be the responsibility of the states to set up appropriate programs for regulating and overseeing the quality assurance and manufacturing standards for medications being sold.” ```json [{"@context":"https://schema.org","@type":"NewsArticle","@id":"https://time.com/3931863/medical-marijuana-benefits/","mainEntityOfPage":{"@type":"WebPage","@id":"https://time.com/3931863/medical-marijuana-benefits/"},"headline":"Here's What Science Says About Medical Marijuana","datePublished":"2015-06-23T15:15:05.000Z","dateModified":"2026-05-11T05:02:52.871Z","description":"It’s buyer-beware for medical marijuana users, since the data supporting the benefits of cannabinoids are still in flux, and most marijuana edibles aren’t well labeled","url":"https://time.com/3931863/medical-marijuana-benefits/","keywords":["medicine","Marijuana","Pot","Drugs","medical marijuana","cannabis"],"thumbnailUrl":"https://static.time.com/v3/assets/bltea6093859af6183b/blta09e0bbc53daa690/6987ee135f570fd910b196c7/marijuana-leaf.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","author":[{"@type":"Person","name":"Alice Park","jobTitle":"Senior Correspondent","url":"https://time.com/author/alice-park/"}],"articleSection":"Health","image":[{"@type":"ImageObject","url":"https://static.time.com/v3/assets/bltea6093859af6183b/blta09e0bbc53daa690/6987ee135f570fd910b196c7/marijuana-leaf.jpg?branch=production&width=1200&quality=75&auto=webp&crop=1200:675&height=675","width":1200,"height":675,"headline":"Marijuana leaf on a white background","caption":"Marijuana leaf on a white background","creditText":"Getty Images","representativeOfPage":true}],"publisher":{"@type":"Organization","name":"Time","url":"https://time.com/","logo":{"@type":"ImageObject","url":"https://time.com/images/logo.png","width":528,"height":156},"foundingDate":"March 3, 1923","sameAs":["https://www.facebook.com/time","https://www.instagram.com/time/?hl=en","https://twitter.com/time","https://www.pinterest.com/timemagazine"]}},{"@context":"https://schema.org","@type":"BreadcrumbList","itemListElement":[{"@type":"ListItem","position":1,"item":{"@id":"/section/health/","name":"Health"}},{"@type":"ListItem","position":2,"item":{"@id":"/tag/medicine/","name":"medicine"}},{"@type":"ListItem","position":3,"item":{"@id":"https://time.com/3931863/medical-marijuana-benefits/","name":"Here's What Science Says About Medical Marijuana"}}]}] ```