AAN Logo Marijuana apparently has a mild benefit on pain, bladder dysfunction and spasticity in multiple sclerosis (MS) patients. Well, this pain reliever also seems to have a negative impact on individuals suffering from this auto-immune disease. In a major breakthrough, experts found that marijuana damages thinking skills in MS patients.

The study was conducted on two groups of 25 people each between the ages of 18 and 65 diagnosed with MS. While one group used marijuana, the other did not. Investigators assayed urine tests to confirm use or non-use of the drug. Both the groups were matched so there would not be significant differences due to age, gender, level of education, IQ before diagnosis, level of disability and duration of time with MS. On an average, the duration of marijuana use appeared 26 years.

“Given that about 40 to 60 percent of MS patients have problems with cognitive function to begin with, any drug that may add to this burden is cause for concern. This study provides empirical evidence that prolonged use of inhaled or ingested marijuana in MS patients is associated with poorer cognitive performance, and these effects have to be weighed against any possible benefit of using marijuana for medicinal purposes,” said study author Anthony Feinstein, MPhil, MD, PhD, with Sunnybrook Health Services Center and the University of Toronto in Ontario, Canada.

Scientists found that 72 percent of users smoked marijuana everyday and 24 percent were weekly users, while one person was a bi-weekly user. Also the cognitive skills of the study subjects were thoroughly examined. Those who smoked marijuana possibly performed significantly worse with respect to attention, speed of thinking, executive function and visual perception of spatial relationships between objects. Marijuana users apparently were twice as likely as non-users to be classified as globally cognitively impaired, defined as impairment on two or more aspects of intellectual functioning.

The study is published in the March 29, 2011, print issue of Neurology.