Cannabis, the genus of the plant known popularly as marijuana, was used as medicine in many cultures for as long as 3,000 years. American physicians employed a liquid extract to treat labor pains, asthma, nervous disorders and even colicky babies. But it was banned from medical use in the United States in 1942 and remained off-limits until individual states began to legalize medical marijuana in recent years.
Despite the ban, the multiple health benefits of cannabis have long been recognized. In fact, in a 1999 publication “Marijuana and Medicine: Assessing the Science Base,” the respected Institute of Medicine concluded that evidence supports the effectiveness of cannabinoids – the active components of the plant – for pain relief, control of nausea and vomiting, and appetite stimulation.
I discussed your question with Donald Abrams, M.D., chief of Hematology-Oncology at San Francisco General Hospital, who directs an integrative oncology consultative practice at the UCSF Osher Center, and who has probably conducted more research on the therapeutic effects of marijuana than anyone in the U.S. Dr. Abrams has shown clinically that inhaled cannabis can reduce the difficult pain associated with nerve damage (neuropathy) and appears to boost the effect of opiate pain relievers. He also tells me that his cancer patients (who have had access to medicinal cannabis in California since 1996) report its effectiveness for relieving chemotherapy-related nausea and increasing appetite. Many patients also find certain strains useful to promote sleep. The difference between strains and their effects has to do with their particular concentrations of cannabinoids, including tetrahydrocannabinol (THC) and cannabidiol (CBD). While THC is psychoactive, CBD is not, but the latter does combat inflammation and pain. For this reason, patients seeking pain relief and sedation may choose a variety that is enriched for CBD over THC.
CBD and CBD oil received a lot of media coverage after Sanjay Gupta M.D., chief medical correspondent at CNN, reported in 2013 that it may reduce epileptic seizures (clinical trials are ongoing). He also stated publicly that he had changed his position on medical marijuana – impressed with the strength of scientific evidence, Dr. Gupta now endorses it.
Another neurologic problem that seems to respond positively to cannabis treatment is multiple sclerosis. Here, THC and CBD seem to alleviate both pain and spasticity. Other cannabinoids remain to be evaluated for their clinical potential.
Legally, however, cannabis is classified as a Schedule I substance, which means it is regarded as having a high potential for abuse and no accepted medical use. This is completely at odds with scientific fact, and its potential for abuse is low. In a 2014 series of editorials, the New York Times rated marijuana as one of the substances with lowest risk of addiction, especially when compared to tobacco and alcohol.
Although its historical record of safe use is unparalleled, one of the drawbacks of using cannabis is that some people react badly to its psychoactivity. Instead of feeling mildly euphoric and experiencing less pain or nausea, they become groggy, anxious, or paranoid. Because cannabis can lower blood pressure and increase pulse rate, Dr. Abrams advises that people with heart conditions and the elderly should use it with caution. He also recommends that adolescents should steer clear of it until their brains are fully developed, which doesn’t happen until the early 20s.
The only real downside of smoking cannabis appears to be an increased risk of bronchitis, which may decrease if the drug is delivered via vaporization. Those who feel that edible cannabis products may be safer than inhaling the drug should be aware that the onset of the effect is delayed, and dosing can be less predictable. In addition, edible cannabis products may have a more profound and prolonged psychoactive effect than inhaled ones.
For an in-depth and highly readable summary of the potential health benefits of marijuana and how it works in the body, Dr. Abrams and I recommend the book, Marijuana Gateway to Health: How Cannabis Protects Us from Cancer and Alzheimer’s Disease, by journalist Clint Werner.
Andrew Weil, M.D.
Originally published 10/03/2014.