1. Slow and stop cancer cells from spreading
It was found in the study, published in the journal Molecular Cancer Therapeutics, that Cannabidiol has the ability to stop cancer by turning off a gene called Id-1.  In 2007, researchers at California Pacific Medical Center in San Francisco, reported that CBD may prevent cancer from spreading. The researchers experimented on breast cancer cells in the lab that had high level of Id-1, and treated them with cannabidiol.
The outcome was rather positive, the cells had decreased Id-1 expression, and were less aggressive spreaders. In fact, the American Association for Cancer Research has found that marijuana actually works to slow down tumor growth in brain, breast, and lungs considerately.
2. Prevent Alzheimer’s
THC, the active ingredient present in marijuana slows the progression of Alzheimer’s disease, a 2006 study led by Kim Janda of the Scripps Research Institute found out. THC slows the formation of amyloid plaques by blocking the enzyme in the brain that makes them. These plaques kill the brain cells, and potentially lead to Alzheimer’s disease
3. Treat Glaucoma
Marijuana can be used to treat glaucoma, which increases the pressure in the eyeball, injuring the optic nerve and causing loss of vision. According to National Eye Institute, marijuana lowers the pressure inside the eye,
“Studies in the early 1970s showed that marijuana, when smoked, lowered intraocular pressure (IOP) in people with normal pressure and those with glaucoma.”
These effects of the drug can prevent blindness.
4. Relieve Arthritis
In 2011, researchers reported that cannabis reduces pain and inflammation, and promotes sleep, which may help relieve pain and discomfort for people with rheumatoid arthritis.
Researchers of the rheumatology units at several hospitals gave their patients Sativex, a cannabinoid-based pain-relieving medicine. After two weeks, patients on Sativex had a significant reduction in pain, and improved better sleep quality compared to placebo users.
5. Control Epileptic seizure
A 2003 study showed that marijuana use can control epileptic seizure.
Robert J. DeLorenzo, of Virginia Commonwealth University, gave marijuana extract and synthetic marijuana to epileptic rats. The drugs stopped the seizures in about 10 hours.
It is found out that the THC controlled the seizures by binding the brain cells responsible for controlling excitability and regulating relaxation. The results were published in the Journal of Pharmacology and Experimental Therapeutics.
6. Ease the pain of multiple sclerosis
Marijuana works to stop the negative neurological effects and muscle spasms caused by multiple sclerosis. A study published in the Canadian Medical Association suggests that marijuana may ease painful symptoms of multiple sclerosis.