Does Pot Use Hamper Thinking in MS?

Study: Multiple Sclerosis Patients Who Smoke Marijuana May Have Slower Reaction Times

Medically Reviewed by Louise Chang, MD on February 13, 2008

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.

Show Sources


Ghaffar, O. Neurology, Feb. 13, 2008; advance online edition.

News release, American Academy of Neurology.

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