On screen text: Pot and MS
Dr. Anthony Feinstein: We had some data from a few years back showing
that MS patients who smoked cannabis possibly had greater cognitive
impairment than you'd anticipate, so there was this idea that lay dormant for
a while and we wanted to go and explore it.
It's a field where there's not a whole lot of data, so these
questions crop up all the time, you know, what effect might cannabis have on MS
patients? Is it beneficial? Is it harmful? And we don't really know, so there was just the
inquiry in that regard. And then
I've always had a belief that cannabis, from a behavioural point of view, is actually quite
harmful, um, the data from the general population
show that its linked to psychosis and mental health disturbance,
and so there was a concern that this might be applicable to MS patients as well, because MS[4] was a large part of my clinical
practice. I wanted to investigate the problem.
On screen text: Main findings.
So we found that the MS patients who use cannabis as opposed to those who did not were more likely
to have cognitive difficulties. Now, to give you a
background sketch: MS by itself is associated with
cognitive problems, so 40 to 60 percent of MS patients
would have cognitive difficulties, even in the absence of cannabis. But what we
found was that patients who smoked cannabis, that
the chances of developing cognitive difficulties went up, and these cognitive
problems were really quite wide-ranging, including information
processing speed impairments, executive function
difficulties, visual spatial problems,
and global cognitive impairment was also higher in this group
as well. So executive function really refers to how you use
your information in a practical way in terms of day to day living
and those are the areas where the impediments were most
marked, in terms of executive function--the speed at which you think, the speed at which you
process information. That seemed to take a bigger hit in the patients
using cannabis. The practical implications of that are as
follows: that patients who are cognitively impaired have more trouble at work,
they have greater difficulty in their day to day relationships, managing everyday activities,
socializing, etcetera. So, cognitive problems by themselves
are not just some abstract finding, but they also are
tightly correlated with some very real world deficits as well--
real world problems--and it appears that cannabis
could clearly make that worse. So I think we have to be careful how we interpret
this study, because a group of patients
we studied were those who had used cannabis every day,
usually every day, often for many years, so you have to
bear in mind that it is a very particular group of patients who
we tested. Having said that, there are some patients who perhaps
have more advanced MS, who are not working, whose
social tasks are not as onerous, who might
benefit from cannabis in terms of pain or spasticity
and I listen to patients when they tell me that. But for the younger
patient who's working, who might be struggling cognitively, and is using
cannabis on a regular basis, it would be a very firm recommendation from
me that they stop using the cannabis. I see it as harmful in that
subgroup of patients. On screen text: In this study, patients using pot DOUBLED their level of cognitive impairment.
So in terms of the future, where do we go with this?
Well, I think it would be good if other study groups outside of
Sunnybrook tried to replicate these findings.
Remember that our data are just based on 25 cannabis
smokers and 25 non-cannibis smokers, that's not a huge sample.
Nevertheless, I think the cognitive data are quite robust, so we're moving on to
another study which is funded by the Multiple Sclerosis Society of Canada, looking
at brain changes in MS patients who use cannabis
and how these brain changes might relate to cognition. So we're going to be starting
that study in the next couple of months, and if indeed we can show that cannabis
smokers have a different pattern of brain activation when it comes to
cognitive tasks, then it really solidifies the
data from the study, it kind of firms up our conclusions, so
I think brain imaging offers us that opportunity to do that.
I think it's important to realize that our data is only applicable to patients who smoke
cannabis, so the street cannabis. We didn't look at the
synthetic cannabis, or drugs like Sativex, which is the cannibis spray.
Patients who are taking those medications were not part of the study. We
confined our sample recruitment just to patients
who are smoking cannibis. I think one patient ingested cannibis, but the majority
smoked. The research in the study was completed by one of my Master's
students, Kimia Honarmand, and she did it as part of her
Master's program, and she was responsible for the data collection,
the data analysis, and she did a very fine job with this. On screen text: To receive a copy of this study contact
The American Academy of Neurology by emailing ababb@aan.com. To review news releases about this study visit: http://sunnybrook.ca/media and www.aan.com/go/pressroom