Results
Despite the dearth of publications on the topic of marijuana, only one small study met the above criteria but the data were presented in such a poor fashion that the scientists could not extract any meaningful data for analysis.
The single study data was not only insufficient but the results showed no effects of marijuana on individuals with dementia. Analysis of the data found that marijuana did not improve behavior, symptoms of dementia nor did it improve mental performance or cognition. The conclusion was that more randomized double-blind placebo controlled trials are needed to determine whether marijuana is clinically effective in the treatment of dementia.
Conclusion
To date, there is no evidence that cannabinoids are effective in the improvement of altered behavior in dementia or in the treatment of symptoms of dementia. One has to remember that marijuana has been smoked for hundred of years and by millions of individuals. Yet the incidence of dementias has not diminished and in fact, there is a rise in the numbers of people with various dementias. There are many anecdotal case reports indicating that individuals who have smoked marijuana usually tend to develop earlier and more severe brain impairment. Just because a substance mimicking marijuana is found in the brain does not automatically mean that it will have a therapeutic benefit. The brain is complex and we still do not know a lot about the brain- the one thing we do know, however, is that smoking marijuana is not good for general health.
http://mrw.interscience.wiley.com/cochrane/clsysrev/articles/CD007204/frame.html