Can Marijuana Prevent Alzheimer's?

Cognitive decline is the No. 1 fear among Americans older than 50, but while we know that exercise, proper diet and social and educational engagement can help maintain brain health, there is as yet no intervention that can fully prevent the onset of dementia or Alzheimer's disease.

If no such development occurs, the number of Americans with Alzheimer's disease is expected to triple in the next 50 years. And while there has been hope that natural remedies could have an impact, none has been shown to be effective so far. When a study released last month proved that ginkgo biloba could not prevent Alzheimer's, one researcher called it the "nail in the coffin" for that theory.

(MORE: The U.S. vs. Alzheimer's: The Fight Heats Up)

Could marijuana be the answer?
 
Cannabinoids, the active chemical components of marijuana, can regulate inflammation in the brain and promote neurogenesis — the growth of new neural pathways — even in cells damaged by age or trauma. As more research has indicated that brain inflammation appears to be a cause of several degenerative diseases, marijuana has been getting a closer look as a potential preventive medication.
 
In a 2006 study published in Molecular Pharmaceutics, a team of University of Connecticut researchers reported that THC, the chemical compound responsible for marijuana's high, “could be considerably better at suppressing the abnormal clumping of malformed proteins that is a hallmark of Alzheimer’s disease than any currently approved prescription.” The research team predicted that cannabinoid-based medications "will be the new breakout medicine treatments of the near future.”
 
To be clear, most scientists investigating the link between cannabinoids and brain health are not advocating widespread casual marijuana smoking to ward off Alzheimer's disease. Marijuana possession remains illegal and research has shown that long-term, frequent marijuana use can impair memory, focus and decision-making.

However, new treatments that can reproduce, through natural or synthetic means, some of the beneficial effects of cannabinoids could hold promise. In 2007, Ohio State University researchers published a paper stating that medications which can stimulate cannabinoid receptors in the brain "may provide clinical benefits in age-related diseases that are associated with brain inflammation, such as Alzheimer’s disease." In 2009, Italian and Israeli researchers found that cannabidiol (CBD), marijuana’s primary non-psychoactive cannabinoid, may also block the formation of the plaques in the brain believed to bring on Alzheimer’s.

(MORE: While Marijuana Endures, Prescription Pills Emerge as a Killer)

Cannabinoid researchers see other potential benefits as well. “In animal models of diseases, the onset and severity of arthritis, Crohn’s disease, Alzheimer’s disease, arteriosclerosis and many cancers" are limited by cannabinoids, says University of Colorado biology professor Robert Melamede, who is also the president of the medical research and development company Cannabis Science. “Appropriate cannabis use reduces biological harm caused by biochemical imbalances, particularly those that increase in frequency with age. Proper cannabis use, as distinguished from misuse, may have significant positive health effects.”
 
For Treatment, a Puff May Be Enough
 
Gary Wenk, a professor of neuroscience at Ohio State and an expert on chronic brain inflammation and Alzheimer’s, says that he began studying cannabinoids after other sorts of compounds sent to him for review by pharmaceutical companies consistently failed to reduce inflammation in the brain. In experiments with rats, he says, marijuana has proven to be the most potent brain anti-inflammatory available. Wenk and his team have also surveyed dementia-free older people about their lifestyles and, he says, discovered that "individuals who smoked marijuana in the ‘60s and ‘70s, who are now entering their 60s and 70s, are not getting Alzheimer’s at the rate they should be."
 
Wenk believes that, in humans, "the equivalent of one puff a day” could help ward off dementia. “I have said to older people, ‘Try it,’” Wenk says. “They email me back to say it’s helping. It’s worked in every rat we’ve given it to. We have some happy, intelligent old rats.”

In a YouTube talk, "Marijuana and Coffee Are Good for the Brain," which has been viewed more than 84,000 times, Wenk envisions a cannabinoid medication people might take "via a patch, so you wouldn't actually have to inhale any cancerous smoke, and you wouldn't have to prepare the cigarettes. We could get around all of those behaviors that some people find unpleasant, especially the elderly." He says he'll continue to search for "a magic bullet" to deliver cannabinoids "to reduce the inflammation and its consequences on your mental function without having to raise the specter of it being a drug of abuse."

Potential for Abuse
 
For the 10 percent of marijuana users who become addicted, a single puff can never be enough. The federal Drug Enforcement Agency considers marijuana to be a Schedule I Controlled Substance with “a high potential for abuse.” The National Institute on Drug Abuse calls marijuana “the most commonly abused illicit drug in the United States.” And in a recent National Survey on Drug Use and Health report, medical marijuana, which can be legally prescribed in 17 states and the District of Columbia for the relief of chronic pain associated with cancer treatment, AIDS and other conditions, was the most abused prescription drug among people over 50.

"Someone who smokes marijuana every day may be functioning at a suboptimal intellectual level all of the time," the institute warns.

Well aware of these concerns, researchers continue to work to isolate marijuana’s beneficial components from its addictive ones. Israeli researchers recently developed cannabis plants that have no THC, but retain robust amounts of CBD, raising hopes for developing cannabinoid medications that deliver no high and carry no risk of addiction. Such drugs could potentially be used not only to help prevent Alzheimer's but also to treat anxiety, depression, Huntington's disease and other maladies.

Two cannabinoid-based medications for nausea, Marinol and Cesamet, have already been approved for use. Sativex, a mouth spray with plant-derived THC and CBD that treats spasticity, cancer pain and neuropathic pain, is available in Canada and parts of Europe; it's presently under an investigational new drug application in the United States.
 
Receptive to Cannabinoids?
 
In discussing their 2006 paper on the potential benefits of THC-based therapies, the University of Connecticut research team wrote, “As the science supporting the validity of endocannabinoid therapeutics progresses, the criminalization of marijuana and the repressive position of the U.S. government is becoming increasingly absurd.”

(MORE: Can the Nation Support Boomers' Mental Health Needs?)

The federal government has given no indication that marijuana will be legalized anytime soon, although national polls indicate that a majority of Americans might support a change in policy. Until then, though, the 3 million American adults over 50 who use marijuana without a prescription do so in violation of the law. Those users, and many other baby boomers, are open to legalization and may be expected to advocate at least for additional medical uses of cannabinoids.

“Boomers are the first generation that’s been exposed to all the weird chemicals in our food and environment," says Martin Lee, author of Smoke Signals: A Social History of Marijuana — Medical, Recreational and Scientific (Scribner, 2012). "It’s like a massive experiment has been done on us — and all of this stuff is taking its toll, health-wise.

"The fact that baby boomers came of age with marijuana makes them receptive" to cannabis-derived treatments, he adds. "We’re the first generation that is less healthy than the generation that preceded us and we’re turning to alternatives."