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Source: GW Pharmaceuticals.

One of the most contentious debates surrounding medical marijuana is whether its use could help millions of people suffering from schizophrenia. For decades, the conventional wisdom has been that marijuana, at a minimum, triggers the disease, or at a maximum, causes it. However, research conducted over the past decade is prompting many to question that long-standing belief.

That research has found that while THC, the marijuana cannibinoid responsible for the "high," can hasten the onset of schizophrenia, CBD, another marijuana cannibinoid, may reduce symptoms. That research has compelled U.K. drugmaker GW Pharmaceuticals (NASDAQ:GWPH) to develop a synthetic variation of CBD that it is studying in clinical trials as a schizophrenia treatment.

First, a bit of background
According to the U.S. National Institute of Mental Health, 1.1% of U.S. adults have schizophrenia.

Schizophrenia requires chronic care and can be debilitating to patients. Those suffering from the disease endure difficulties in thinking, perceiving the world around them, and controlling emotional responses. Some patients may have delusions and hallucinations, while others may struggle to form social bonds.

Since schizophrenia is a chronic disease, patient adherence to therapy and medicine is critical. Unfortunately, the nature of the disease makes sticking with treatment regimens tricky.

Current treatment options
According to NIMH research, outpatient spending on prescription antipsychotics (many of which are used to treat schizophrenia) climbed from $1.7 billion in 1997 to $7.4 billion in 2007. That is due to both an increase in prescription volume and rising drug prices. During that period, the number of annual antipsychotic prescriptions jumped 86%, from 17.4 million to 32.4 million, while the average price per prescription climbed 138%, from $96 to $228. According to Express Scripts, mental and neurological disorders such as schizophrenia were the eighth-most costly disease group in the United States last year in terms of per member per year spending.

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Source: Express Scripts

Among the top five drugs by market share, generic Seroquel (quetiapine) is the most commonly prescribed. AstraZeneca lost patent protection on Seroquel in 2012, but maintains patent protection on the extended release Seroquel XR until 2017. Last year, sales of Seroquel XR totaled more than $1 billion.

Another widely used treatment is Otsuka and Bristol-Myers Squibb's Abilify, which holds nearly 15% market share and notched more than $8 billion in sales last year. Although the companies are fighting the threat of generic challengers to the drug's original formula, Otsuka and Bristol-Myers won approval of an extended release formulation in 2013.

Medical marijuana's potential
Express Scripts estimates that 42% of patients taking mental or neurological disorder drugs like atypical antipsychotics fail to take their medicine as prescribed. Since the top five prescribed drugs account for more than 60% of the market, and many of those have been available for a decade or longer, it would seem there's a significant unmet need for better drugs with fewer side effects. GW Pharma hopes that CBD can fill that need.

Based on early studies, the company might be onto something.

In various early stage trials conducted by non-GW Pharma researchers, CBD has been shown to reduce psychosis, depression, and anxiety. In one small study of 39 people with schizophrenia in Germany, for example, patients receiving either CBD or an antipsychotic saw similar improvement over four weeks of treatment.

GW Pharma's own research was encouraging enough to prompt the company to launch a phase 2 trial examining their drug in schizophrenia patients. The company hopes to establish that its purified version of CBD works better than a placebo when used alongside current-generation antipsychotic drugs. If that study goes well, then the company will likely launch a larger, later-stage trial.

Fool-worthy final thoughts
GW Pharma's phase 2a study's estimated primary completion date isn't until August 2015, so It will be a while before we learn the results and even longer before a drug could become commercially available.

Early stage research into the use of CBD as a treatment for schizophrenia is intriguing, but it's far from proven. While CBD therapy could eventually play a role in treating schizophrenia, the purified version of CBD used in GW Pharma's preclinical study isn't the same as what patients could get on the street. Although growers are breeding strains of medical marijuana containing higher levels of CBD, the majority of marijuana remains heavy on THC.

Todd Campbell has no position in any stocks mentioned. Todd owns E.B. Capital Markets, LLC. E.B. Capital's clients may or may not have positions in the companies mentioned. Todd owns Gundalow Advisors, LLC. Gundalow's clients do not have positions in the companies mentioned. The Motley Fool has no position in any of the stocks mentioned. Try any of our Foolish newsletter services free for 30 days. We Fools may not all hold the same opinions, but we all believe that considering a diverse range of insights makes us better investors. The Motley Fool has a disclosure policy.