Though many multiple sclerosis sufferers turn to marijuana for relief of their symptoms, a new study finds that smoking the drug can actually cause problems with emotional responses and memory.

Researchers at the University of Toronto conducted interviews with 140 people who had MS. Ten participants reported they had smoked marijuana in the previous month — they were compared to people who did not smoke marijuana and who were of the same age, sex, and had suffered from MS of equal duration.

Marijuana smokers with MS were 50 per cent slower on tests of information processing speed than those who didn't smoke the drug, the study found.
(CBC)

All participants were assessed for depression, anxiety and other mental health issues. Researchers also tested their cognition skills, such as memory, the speed of processing information and thinking skills.

Marijuana smokers were 50 per cent slower on tests of information processing speed versus those who didn't smoke the drug. They also had a higher incidence of depression and anxiety.

The authors also point out that MS itself causes neuropsychological impairment in 40 to 65 per cent of patients.

"This is the first study to show that smoking marijuana can have a harmful effect on the cognitive skills of people with MS," said study author Anthony Feinstein of the University of Toronto.

"This is important information because a significant minority of people with MS smoke marijuana as a treatment for the disease, even though there are no scientific studies demonstrating that it is an effective treatment for emotional difficulties."

The authors call for more research into the connection between marijuana smoking and cognition issues.

The study was published online Wednesday in the journal Neurology.