Image source: Flickr user Oswaldo.

Marijuana's ascent appears nothing short of unstoppable.

Roughly two decades ago, only a quarter of people responding to a national Gallup poll wanted to see marijuana legalized. But beginning in California in 1996 and spreading throughout the country, 22 additional states, as well as Washington, D.C., have legalized marijuana for medicinal use as of today.

How's this possible? On one hand, public approval of marijuana being used as medicine is higher than it's ever been. A CBS News poll from April 2015 showed that a whopping 84% of those surveyed across America would like to see marijuana legalized for medicinal purposes.

The other part of this equation is that we've been witnessing drug developers and clinical researchers devote more of their energy to the potential benefits of marijuana. New studies have emerged suggesting that marijuana or the cannabinoids found within the cannabis plant may offer assistance in fighting certain diseases and ailments. While the vast majority of these studies are purely correlative at this point -- a fancy way of saying more testing is needed for confirmation -- they nonetheless give a nation of chronically and terminally ill patients hope that they may have another treatment pathway available.

Image source: GW Pharmaceuticals.

Diseases marijuana may successfully fight
With this in mind, let's take a brief look at 15 diseases and ailments that marijuana has, in clinical studies, successfully fought.

Where should we begin? How about with the vastest clinical portfolio backed by cannabinoid-based research: that of GW Pharmaceuticals (GWPH).

1. & 2. Dravet syndrome and Lennox-Gastaut syndrome
Arguably the most exciting compound in GW Pharmaceuticals' pipeline is Epidiolex, a liquid cannabidiol (CBD)-based compound that's been geared to fight two rare forms of childhood-onset epilepsy. In midstage studies for both Dravet syndrome and Lennox-Gastaut, Epidiolex reduced seizure frequency in patients taking the drug by greater than 50%. Epidiolex is currently undergoing two late-stage studies in each indication.

3. Tuberous Sclerosis Complex (TSC)
You didn't think we were done with Epidiolex yet, did you? TSC is a genetic disorder that causes non-malignant tumors to form throughout the body, affecting about 50,000 people in the United States. Epilepsy is the most symptom associated with TSC, and roughly 60% of TSC patients have treatment-resistant seizures. In an expanded access program involving five patients, Epidiolex reduced seizure frequency by 97% for two patients, and by 77% for another at week 16 compared to a four-week baseline period. 

Image source: GW Pharmaceuticals.

4. Spasticity associated with multiple sclerosis
GW Pharmaceuticals also has Sativex, an approved oromucosal spray in 15 countries outside the U.S. that contains CBD and tetrahydrocannabinol, or THC, the hallucinogenic property of marijuana. In clinical studies Sativex was shown to reduce spasticity, or the tightness of muscles, in patients with multiple sclerosis.

5. Type 2 diabetes
How about a disease that the Centers for Disease Control and Prevention estimates 90% to 95% of the 29.1 million diabetics in the United States currently have? GWP42004 from GW Pharmaceuticals was shown in phase 2a studies back in 2012 to deliver statistically significant reductions in fasting plasma glucose levels, improved beta-cell function, and increased insulin sensitivity.

If that's not enough, an abstract published in The American Journal of Medicine in 2013 that studied 4,657 adults between 2005 and 2010 showed that current marijuana use was associated with a 16% reduction in fasting insulin levels and a 17% drop in HOMA-IR, which is a measure of insulin resistance.

Image source: INSYS Therapeutics.

6. Chemotherapy-induced nausea and vomiting & 7. Anorexia for patients suffering weight loss with AIDS
Of course, GW Pharmaceuticals isn't the only show in town. INSYS Therapeutics (INSY) is developing a new formulation of dronabinol in a liquid oral solution, which is based on the cannabinoid THC, for the treatment of nausea and vomiting caused by chemotherapy, as well as anorexia in AIDS patients suffering weight loss. As a reminder, Insys has already received approval from the Food and Drug Administration to sell soft gelatin dronabinol capsules for both treatments listed above, but it's in the process of seeking a new label indication for its oral solution.

And it's not just publicly traded companies delivering the good news, either.

8. Chronic pain
The direct medical and economic costs of dealing with chronic pain are enormous. Based on data from the American Academy of Pain Medicine, medicine costs and productivity losses total $560 billion to $635 billion annually -- and that's based on 2010 dollars. However, a study published in the Journal of Pain this past September from Canadian researchers showed that marijuana had comparable efficacy to chronic pain medicines already on the market, but a markedly better safety profile since no one has overdosed and died from marijuana.

9. Organ transplant rejection
How about this: researchers at the University of South Carolina School of Medicine took genetically different mice and transplanted grafts of skin from one group onto the other, attempting to induce transplant rejection. One group was given a placebo, while another was given THC. The group of mice given THC demonstrated delayed rejection of the skin graft by purportedly suppressing the immune system response of the mice.

Image source: Flickr user Loren Kerns.

10. Alzheimer's disease
Another potential benefit? How about treating Alzheimer's patients, of which there are about 5 million today, per the Alzheimer's Association. An abstract report published in the Journal of Alzheimer's Disease showed that at the six-hour, 24-hour, and 48-hour time marks THC lowered beta-amyloid levels in a dose-dependent manner. Beta-amyloid plaques are what stick to the brains of Alzheimer's patients, resulting in progressive cognitive decline.

11. Brain cancer
Even extremely difficult-to-treat diseases have demonstrated positive responses to the use of cannabinoids. In May 2014, London researchers noted that pretreating brain tumors with CBD and THC prior to radiation therapy increased sensitivity to the radiation, thus improving its effectiveness. In studies, tumors pretreated with CBD and THC wound up being just one-tenth the size of tumors in the control group.

12. Schizophrenia
Schizophrenia is a disorder that's diagnosed in about 3.5 million Americans and costs between $32.5 billion and $65 billion to treat annually. However, a 2012 study published in Translational Psychiatry showed that CBD may prove an attractive alternative to standard antipsychotic medication. A trial consisting of 39 patients (20 on CBD and 19 on amisulpride) showed that while both led to similar Brief Psychiatric Rating Scale scores at the end of the study, fewer side effects were seen in the CBD group. 

13. Parasitic infections
A study unearthed last year involving an anthropologist named Dr. Edward Hagen from Washington State University in Vancouver looked at 379 Aka pygmies in Africa's Congo Basin, 95% of whom had worm-based parasitic infections, and many of whom smoked marijuana regularly. Dr. Hagen's findings showed that a lower number of parasitic worms were found in adult Aka with higher concentrations of THCA (a byproduct of THC) in their urine.

Image source: Pixabay.

14. Glaucoma
If there's one indication where marijuana is regularly prescribed across the 23 legal marijuana states, it's glaucoma, a disease that can increase pressure within the eyeball, damaging the optic never and causing vision loss. According to the National Eye Institute, marijuana lowers intraocular pressure associated with glaucoma, which may help slow progressions of the disease.

15. Inflammatory bowel diseases
Lastly, marijuana was shown in a study by the University of Nottingham in 2010 to play a critical role in immune responses of the gastrointestinal tract, which could lead to treatments for various forms of inflammatory bowel diseases. As published in the Journal of Pharmacology and Experimental Therapeutics, an in-vitro model utilizing cannabinoids CBD and THC showed tighter bonding of intestinal cells, helping to keep bacteria out, and, in theory, easing symptoms likely associated with inflammatory bowel diseases.  

Keep in mind, once again, that quite a few of these studies are still in the early stages, and that additional studies are needed to concretely prove that marijuana offers these supposed clinical benefits.

Nonetheless, the treatment potential of marijuana and its cannabinoids is intriguing, and it might be worth keeping a close eye on the company with the most robust cannabinoid-based treatment pipeline, GW Pharmaceuticals. It's certainly not without risks -- it's losing money right now, and that trend is likely to continue for many years to come. However, if cannabinoids do indeed have the tools necessary to treat a host of disease and ailments, then GW Pharmaceuticals could one day become wildly successful.