Yes, the Drug Enforcement Agency still categorizes marijuana as a schedule I drug, one that has no accepted medical use, but since the late 1990s, a majority of Americans have thought medical pot should be legal. A majority support recreational legalization as well.

33 states have legalized medical marijuana (that number is even higher, no pun intended, if we count laws with very limited access).

But what do we know about the science behind medical uses of cannabis?

There seem to be some definite benefits. Even the NIH’s National Institute on Drug Abuse lists medical uses for cannabis.

Yet it’s hard to study marijuana’s uses while the schedule I classification remains in place. It makes it difficult for researchers to get their hands on pot grown to the exacting standards that are necessary for medical research. Plus, there are hundreds of chemical compounds in the cannabis plant that could play a role in medical treatments, but for now, it’s hard to know which aspect of the plant is causing an effect.

Using all the compounds in marijuana simultaneously is like “throwing 400 tablets in a cocktail and saying ‘take this, a professor of neuroscience and psychiatry at Icahn School of Medicine at Mount Sinai, told Tech Insider last summer.

More research would identify health benefits more clearly and would also help clarify potential dangers. As with any psychoactive substance, there are risks associated with abuse, including dependency and emotional issues. Many doctors want to understand marijuana’s effects better before deciding whether to recommend it or not.

Marijuana use can prevent epileptic seizures in rats, a 2003 study showed.

We gave extract and synthetic marijuana to epileptic rats. The drugs rid the rats of the seizures for about 10 hours. Cannabinoids like the active ingredients in marijuana, tetrahydrocannabinol (also known as THC), control seizures by binding to the brain cells responsible for controlling excitability and regulating relaxation.

More recent human studies have shown that cannabidiol (CBD), another major marijuana compound, seems to help people with treatment-resistant epilepsy.

There’s a fair amount of evidence that marijuana does no harm to the lungs, unless you also smoke tobacco, and one study published in Journal of the American Medical Association found that marijuana not only doesn’t impair lung function, it may even increase lung capacity.

Researchers looking for risk factors of heart disease tested the lung function of 5,115 young adults over the course of 20 years. Tobacco smokers lost lung function over time, but pot users actually showed an increase in lung capacity.

It’s possible that the increased lung capacity may be due to taking a deep breaths while inhaling the drug and not from a therapeutic chemical in the drug.

Those smokers only toked up a few times a month, but a more recent survey of people who smoked pot daily for up to 20 years found no evidence that smoking pot harmed their lungs.

During the research for his documentary who treats their 5-year-old daughter using a medical marijuana strain high in cannabidiol and low in THC.

There are at least two major active chemicals in marijuana that researchers think have medicinal applications (there are up to 79 known active compounds). Those two are cannabidiol (CBD) — which seems to impact the brain mostly without a high— and tetrahydrocannabinol (THC) — which has pain relieving (and other) properties.

The family’s daughter, Charlotte, has Dravet Syndrome, which causes seizures and severe developmental delays.

According to the film, the drug has decreased her seizures from 300 a week to just one every seven days. Forty other children in the state are using the same strain of marijuana (which is high in CBD and low in THC) to treat their seizures — and it seems to be working.

The doctors who recommended this treatment say that the cannabidiol in the plant interacts with the brain cells to quiet the excessive activity in the brain that causes these seizures.

As notes, a hospital that specializes in the disorder, the American Academy of Pediatrics, and the Drug Enforcement agency don’t endorse marijuana as a treatment for Dravet or other seizure disorders.

CBD may also help prevent certain cancers from spreading, researchers reported in 2007.

Cannabidiol stops cancer by turning off a gene called Id-1, the study, published in the journal Molecular Cancer Therapeutics, found. Cancer cells make more copies of this gene than non-cancerous cells, and it helps them spread through the body.

The researchers studied breast cancer cells in the lab that had high expression levels of Id-1 and treated them with cannabidiol. After treatment the cells had decreased Id-1 expression and were less aggressive spreaders. But beware: these are studies on cancer cells in the lab, not on cancer patients.

Other very preliminary studies on aggressive brain tumors in mice or cell cultures have shown that THC and CBD can slow or shrink tumors at the right dose, which is a great reason to do more research into figuring out that dose says one medical marijuana doctor in Florida.

One 2014 study found that marijuana can significantly slow the growth of the type of brain tumor associated with 80% of malignant brain cancer in people.

In “WEED,” also mentioned a few studies in the US, Spain, and Israel that suggest the compounds in cannabis could even kill cancer cells.

Medical marijuana users claim the drug helps relieve pain and suppress nausea — the two main reasons it’s often used to relieve the side effects of chemotherapy.

In 2010, researchers at Harvard Medical School suggested that that some of the drug’s benefits may actually be from reduced anxiety, which would improve the smoker’s mood and act as a sedative in low doses.

Beware, though, higher doses can increase anxiety and make you paranoid.

Marijuana may be able to slow the progression of Alzheimer’s disease, a study led by Kim Janda of the Scripps Research Institute suggests.

The 2006 study, published in the journal Molecular Pharmaceutics, found that THC, the active chemical in marijuana, slows the formation of amyloid plaques by blocking the enzyme in the brain that makes them. These plaques seem to be what kill brain cells and potentially cause Alzheimer’s.

A synthetic mixture of CBD and THC seem to preserve memory in a mouse model of Alzheimer’s disease. Another study suggested that in population-based studies, a THC-based prescription drug called dronabinol was able to reduce behavioral disturbances in dementia patients.

All these studies are in very early stages, so more research is needed.

Cannabis may ease painful symptoms of multiple sclerosis, a study published in the Canadian Medical Association Journal suggests.

She studied 30 multiple sclerosis patients with painful contractions in their muscles. These patients didn’t respond to other treatments, but after smoking marijuana for a few days they reported that they were in less pain.

The THC in the pot binds to receptors in the nerves and muscles to relieve pain. Other studies suggest that the chemical also helps control the muscle spasms.

Other types of muscle spasms respond well to medical marijuana as well. Gupta also found a teenager who was using medical marijuana to treat diaphragm spasms that were untreatable by other, prescribed and very strong, medications.

His condition is called myoclonus diaphragmatic flutter (also known as Leeuwenhoek’s Disease) and causes nonstop spasming in the abdominal muscles which are not only painful, but interfere with breathing and speaking says on marijuana doctor who specializes in the field of medical cannabis.

Smoking marijuana was able to calm the attacks almost immediately, at least it seemed to in this patient.

Marijuana use may help treat the eye disease glaucoma, which increases pressure in the eyeball, damaging the optic nerve and causing loss of vision, though there are questions about how effective it really is.

Marijuana decreases the pressure inside the eye, according to the National Eye Institute: “Studies in the early 1970s showed that marijuana, when smoked, lowered intraocular pressure (IOP) in people with normal pressure and those with glaucoma” — though they still said that pharmaceutical drugs were more effective.

For now, at least, the medical consensus is that marijuana only lowers IOP for a few hours. Researchers hope that perhaps a marijuana-based compound could be developed that lasts longer.

Patients with inflammatory bowel diseases like Crohn’s disease and ulcerative colitis could benefit from cannabis use, studies suggest.

Researchers found in 2010 that chemicals in marijuana, including THC and cannabidiol, interact with cells in the body that play an important role in gut function and immune responses. The study was published in the Journal of Pharmacology and Experimental Therapeutics.

THC-like compounds made by the body increase the permeability of the intestines, allowing bacteria in. The plant-derived cannabinoids in marijuana block these body-cannabinoids, preventing this permeability and making the intestinal cells bond together tighter.

One study in Israel showed that smoking a joint significantly reduced Crohn’s disease symptoms in 10 out of 11 patients compared to a placebo and without side effects.

That’s a small study, but other research has shown similar effects. Even more research finds that people with Crohn’s and other inflammatory bowel disorders use cannabis to help deal with their symptoms, even if there are questions about how much marijuana can or can’t help.