Pavisian B, Macintosh BJ, Szilagyi G, Staines RW, O’Connor P, Feinstein A.Effects of cannabis on cognition in patients with MS: A psychometric and MRI study. Neurology. 2014 Apr. [Epub ahead of print]
OBJECTIVE: To determine functional and structural neuroimaging correlates of cognitive dysfunction associated with cannabis use in multiple sclerosis (MS). the N-Back. Resting-state fMRI and structural MRI data (lesion and normal-appearing brain tissue volumes, diffusion tensor imaging metrics) were also collected. Neuropsychological data pertaining to verbal and visual memory, information processing speed and attention were obtained.
METHODS: 20 subjects with MS who smoked cannabis and 19 non-cannabis users with MS, matched on demographic and neurologic variables, underwent fMRI while completing a test of working memory,
RESULTS: The cannabis group performed more poorly on the more demanding test tasks (p < 0.05). Cannabis users had more diffuse cerebral activation and made more errors on the 2-Back task (p < 0.006), during which they displayed increased activation relative to non-users in parietal (p < 0.007) and anterior cingulate (p < 0.001) regions implicated in working memory. No group differences in resting-state networks or structural MRI variables were found.
CONCLUSIONS. Patients with MS who smoke cannabis are more cognitively impaired than non-users. Cannabis further compromises cerebral compensatory mechanisms, already faulty in MS. These imaging data boost the validity of the neuropsychological findings and act as a cautionary note to cannabis users and prescribers.
Whilst I doubt we have many doctors prescribing non-medicinal formulated cannabis, there are plenty of Pot-Docs in the USA supplying the cannabis plant.
Are they just stoners or are the self-medicating?
Having spent years demonising tobacco smoking it seems a rather weird idea to be now legalising smoking of cannabis, as is occurring in a few states of the US so far.
There are clearly health issues with smoking, but I think we can agree there are a few with MS too and some people claim there is benefit to be had from marijuana and particularly smoked cannabis.
This sort of makes some sense as it is easier to dose-titrate than say the oral route, it avoids drug breakdown associated with eating cannabis heating converts the THC-acids into THC, the active ingredient and can get you intoxicated quicker.
In this study cannabis smokers did worse on a number of behavioural tests than non-smoking MSers which is perhaps not surprising as you can’t dissociate the potential adverse effects away from the benefit of smoking cannabis.