Does Pot Use Hamper Thinking in MS?

Feb. 13, 2008 -- New research shows that among multiple sclerosis patients, those who smoke marijuana may have slower reaction times on mental skills tests and are more likely to report a history of psychiatric diagnoses.

That news, published in today's advance online edition of Neurology, comes from a Canadian study.

The researchers studied 140 multiple sclerosis patients, including 10 who said they smoke marijuana at least once a month.

The patients took various mental skills tests and were interviewed about their mental health history.

Marijuana smokers had slower average reaction times on a test that challenged them to process information quickly. And they were more likely to report a history of psychiatric diagnoses, most of which were depression or anxiety diagnoses.

It's not clear if marijuana use caused those conditions. The study doesn't show which came first -- marijuana use or problems with emotions and thinking. It's also not clear if the patients, who all attended the same outpatient clinic, are representative of all MS users.

But in a news release, researcher Anthony Feinstein, MPhil, PhD, FRCP, states that "this is important information because a significant minority of people with MS smokes marijuana as a treatment for the disease."

Feinstein conducted the study with Omar Ghaffar, MD, FRCP. Both work in the psychiatry department at the Sunnybrook Health Sciences Centre in Toronto.