This month, we sat down with Dr. John DeLuca and Dr. Robert Fox to discuss your questions about marijuana and MS, as part of our new Discussion of the Month feature. Read our interview about marijuana and cognition with Dr. DeLuca, Senior Vice President of Research & Training at Kessler Foundation, below. And check back tomorrow as we talk with Dr. Fox about how to talk to your doctor about marijuana, whether or not to continue on your other medications, what we know about various forms of cannabis and cannabinoids, and more.
Dr. DeLuca, would you please explain the difference between cannabis and cannabinoids?
Cannabis is the name of the plant that people refer to when they talk about marijuana. Marijuana is more of the lay term, usually associated with the psychoactive form of cannabis. Cannabinoids are the chemical components contained within cannabis the plant. There are approximately 85 cannabinoids in cannabis. The one that people typically think about is THC which is the psychoactive cannabinoid within cannabis.
Cannabinoids activate specific receptors throughout the body, particularly in the nervous system and the immune system, which is where THC would have its psychoactive effect. However, there presumably are other effects that are physiological in nature, because of how they react with the receptors. There is some evidence suggesting that these cannabinoids affect pain sensation, mood, appetite, memory and concentration.
What do we know about some of the short-term cognitive effects of cannabis use?
There are acute effects of cannabis use that have been fairly well recognized in the scientific community. These include decreased reaction time as well as effects on concentration, processing speed and memory performance. It can also have a potential impact on driving. At particularly large doses, cannabis can cause anxiety, depression, even hallucinations and delusions, in addition to more severe cognitive problems. However, it’s important to understand that there are no simple answers for every single individual – it depends on a number of factors.
And what about research on cannabis and cognition specifically related to people with MS?
There have been a few studies on persons with MS – one of which was recently published in 2014. The majority of study results have been consistent in that they suggest an impact on cognitive impairment. These studies involved chronic users compared to non-users, which means that they don’t tell us much about people who use cannabis on occasion. The primary effects seem to be decreasing processing speed.
Other studies show decreases in working memory executive functioning, visual-spatial perception, and memory. And one study even found a twofold increase in global cognitive dysfunction. So, the research studies to-date pretty consistently show that there are cognitive problems associated with chronic cannabis use. Now, this is important, because this is in a population that is already at risk of cognitive problems. It is really important for people with MS to understand this and consider this when thinking about using it to treat MS symptoms.
Is there anything else you would recommend people who are considering using cannabis to treat some of their MS symptoms to consider?
When you have a disease such as MS that affects the brain, it’s important to consider that THC can have negative consequences on cognition that might be detrimental – specifically on areas of the brain such as the hippocampus (which would involve memory), amygdala (which would involve emotional learning and emotional processing), and prefrontal cortex (which can affect working memory).
On the other hand, some research suggests that cannabis can help with things like pain, or bladder function. I think that the discussion needs to be a weighing of risks and benefits of both cannabis and other treatments that can be utilized to treat the same symptoms. I think that we need more research to find out whether it’s really the THC cannabinoid that is beneficial, or some other cannabinoids within the use of cannabis that might be better for treatment of specific symptoms.
The other important point to consider is if you just get cannabis from the street, you don’t know what’s in it. You don’t know dosage. You don’t know if there is anything other than the cannabinoids which are involved. So, oftentimes people think of marijuana as just marijuana but it varies a lot, and it varies by intensity, dosage, and it varies by cannabinoids that are within it. It’s easy to presume that because cannabis is a plant and it is found in nature, it is not going to have negative effects on you, but more research needs to be done to understand the benefits and side effects.