Within therapeutic doses, no impairment or negative psychological symptoms noted. However, at high dosages, negative psychological symptoms noted.
Link: Psychopathological And Cognitive Effects Of Therapeutic Cannabinoids In Multiple Sclerosis: A Double-blind, Placebo Controlled, Crossover Study
Year: 2009
DOI: 10.1097/WNF.0B013E3181633497
Demonstrable efficacy of cannabis for treatment of Multiple Sclerosis (MS) according to the results found in this study.
Free-dose cannabis plant extract (Sativex)