Just read a study in Neurology about the effects of marijuana in patients with multiple sclerosis. It seems that MS patients who smoke marijuana have more cognitive dysfunction and mood disorders as compared to MS patients that do not. MS patients may be smoking marijuana recreationally or they may be using it to get rid of tingling and other paraesthesias.
Multiple sclerosis itself causes cognitive problems and if patients smoke marijuana it seems they compound them. With the limited data available to us currently, it is probably wise that patients with multiple sclerosis avoid smoking marijuana.
Nitin Sethi, MD
Braindisease's Weblog 