Mental Impairments Found Among MS Patients Who Use Cannabis

Multiple sclerosis patients who smoke marijuana were more likely to have a history of a mental illness and also performed worse on a test of their mental processing speed and working memory, according to results of a community-based study.

The data “provide the first evidence of the injurious effect of inhaled cannabis on the mentation of patients with MS,” the authors wrote in Neurology.

Ascertaining the effect of cannabis use in MS patients is important because cannabis often is used as a therapeutic agent in the disease, and MS is “by itself a cause of neuropsychological impairment in 40%–65% of patients,” wrote Dr. Omar Ghaffar and his colleague, Dr. Anthony Feinstein, both of the Sunnybrook Health Sciences Centre, Toronto, and the University of Toronto.

The researchers looked at 140 consecutive, community-dwelling MS patients seen at an outpatient clinic in Toronto. Three-fourths were women. The disease was relapse-remitting in 82 patients, secondary progressive in 49 patients, and primary progressive in 9 patients (Neurology 2008 [Epub doi:10.1212/01.wnl.0000304046.23960.25]).

Overall, 10 subjects reported current cannabis use (use of inhaled marijuana purchased on the street in the past month). Users and nonusers differed significantly in age (users had a mean age of about 36 years, vs. nonusers, whose mean age was 44.5 years, P =.001). There were no other differences with respect to disease, duration, disability, education, or gender.

“Since age is a factor that could potentially affect cognition independent of cannabis use, the 10 current cannabis users were each age-matched to 4 subjects who did not use cannabis [total control sample n = 40],” wrote the authors. Subjects were then evaluated using the Structured Clinical Interview for DSM-IV Axis I Disorders; the Hospital Anxiety and Depression Scale; and several cognitive assessments.

Overall, the 10 cannabis users were not more likely to have a specific DSM-IV diagnosis (depression, anxiety disorders, alcohol use disorders, etc.), but they were more likely to have had one of those diagnoses in general (P = .04).

There were no differences on the four cognitive measures included in the Neuropsychological Battery for MS. However, on the Symbol Digit Modalities Test (SDMT), cannabis users displayed a significantly slower mean performance time (P = .006). “In the SDMT, nine different symbols, each associated with a number, were presented visually to the subject. Nine symbols at a time were shown to the subject in various orders and the subject had to respond by naming the number that corresponded to each symbol according to the original code,” wrote the authors.

“This test, an index of information processing speed and working memory, has emerged as one of the most sensitive markers of cognitive impairment in MS,” they wrote.

A small sample size was one important limitation to this study. The authors also noted that their reliance on self-reports of cannabis use was not confirmed by urinary toxicology. Finally, cannabis users and nonusers differed slightly in their treatment regimens: More nonusers took disease-modifying treatments while more cannabis users took antidepressants. However, neither of these differences was significant. Furthermore, wrote the authors, “the relation between disease-modifying treatments and cognition remains equivocal, and data [suggest] that patients with MS taking antidepressants are not more impaired on tests such as the SDMT.”

Multiple sclerosis patients who smoke marijuana were more likely to have a history of a mental illness and also performed worse on a test of their mental processing speed and working memory, according to results of a community-based study.

The data “provide the first evidence of the injurious effect of inhaled cannabis on the mentation of patients with MS,” the authors wrote in Neurology.

Ascertaining the effect of cannabis use in MS patients is important because cannabis often is used as a therapeutic agent in the disease, and MS is “by itself a cause of neuropsychological impairment in 40%–65% of patients,” wrote Dr. Omar Ghaffar and his colleague, Dr. Anthony Feinstein, both of the Sunnybrook Health Sciences Centre, Toronto, and the University of Toronto.

The researchers looked at 140 consecutive, community-dwelling MS patients seen at an outpatient clinic in Toronto. Three-fourths were women. The disease was relapse-remitting in 82 patients, secondary progressive in 49 patients, and primary progressive in 9 patients (Neurology 2008 [Epub doi:10.1212/01.wnl.0000304046.23960.25]).

Overall, 10 subjects reported current cannabis use (use of inhaled marijuana purchased on the street in the past month). Users and nonusers differed significantly in age (users had a mean age of about 36 years, vs. nonusers, whose mean age was 44.5 years, P =.001). There were no other differences with respect to disease, duration, disability, education, or gender.

“Since age is a factor that could potentially affect cognition independent of cannabis use, the 10 current cannabis users were each age-matched to 4 subjects who did not use cannabis [total control sample n = 40],” wrote the authors. Subjects were then evaluated using the Structured Clinical Interview for DSM-IV Axis I Disorders; the Hospital Anxiety and Depression Scale; and several cognitive assessments.

Overall, the 10 cannabis users were not more likely to have a specific DSM-IV diagnosis (depression, anxiety disorders, alcohol use disorders, etc.), but they were more likely to have had one of those diagnoses in general (P = .04).

There were no differences on the four cognitive measures included in the Neuropsychological Battery for MS. However, on the Symbol Digit Modalities Test (SDMT), cannabis users displayed a significantly slower mean performance time (P = .006). “In the SDMT, nine different symbols, each associated with a number, were presented visually to the subject. Nine symbols at a time were shown to the subject in various orders and the subject had to respond by naming the number that corresponded to each symbol according to the original code,” wrote the authors.

“This test, an index of information processing speed and working memory, has emerged as one of the most sensitive markers of cognitive impairment in MS,” they wrote.

A small sample size was one important limitation to this study. The authors also noted that their reliance on self-reports of cannabis use was not confirmed by urinary toxicology. Finally, cannabis users and nonusers differed slightly in their treatment regimens: More nonusers took disease-modifying treatments while more cannabis users took antidepressants. However, neither of these differences was significant. Furthermore, wrote the authors, “the relation between disease-modifying treatments and cognition remains equivocal, and data [suggest] that patients with MS taking antidepressants are not more impaired on tests such as the SDMT.”

Multiple sclerosis patients who smoke marijuana were more likely to have a history of a mental illness and also performed worse on a test of their mental processing speed and working memory, according to results of a community-based study.

The data “provide the first evidence of the injurious effect of inhaled cannabis on the mentation of patients with MS,” the authors wrote in Neurology.

Ascertaining the effect of cannabis use in MS patients is important because cannabis often is used as a therapeutic agent in the disease, and MS is “by itself a cause of neuropsychological impairment in 40%–65% of patients,” wrote Dr. Omar Ghaffar and his colleague, Dr. Anthony Feinstein, both of the Sunnybrook Health Sciences Centre, Toronto, and the University of Toronto.

The researchers looked at 140 consecutive, community-dwelling MS patients seen at an outpatient clinic in Toronto. Three-fourths were women. The disease was relapse-remitting in 82 patients, secondary progressive in 49 patients, and primary progressive in 9 patients (Neurology 2008 [Epub doi:10.1212/01.wnl.0000304046.23960.25]).

Overall, 10 subjects reported current cannabis use (use of inhaled marijuana purchased on the street in the past month). Users and nonusers differed significantly in age (users had a mean age of about 36 years, vs. nonusers, whose mean age was 44.5 years, P =.001). There were no other differences with respect to disease, duration, disability, education, or gender.

“Since age is a factor that could potentially affect cognition independent of cannabis use, the 10 current cannabis users were each age-matched to 4 subjects who did not use cannabis [total control sample n = 40],” wrote the authors. Subjects were then evaluated using the Structured Clinical Interview for DSM-IV Axis I Disorders; the Hospital Anxiety and Depression Scale; and several cognitive assessments.

Overall, the 10 cannabis users were not more likely to have a specific DSM-IV diagnosis (depression, anxiety disorders, alcohol use disorders, etc.), but they were more likely to have had one of those diagnoses in general (P = .04).

There were no differences on the four cognitive measures included in the Neuropsychological Battery for MS. However, on the Symbol Digit Modalities Test (SDMT), cannabis users displayed a significantly slower mean performance time (P = .006). “In the SDMT, nine different symbols, each associated with a number, were presented visually to the subject. Nine symbols at a time were shown to the subject in various orders and the subject had to respond by naming the number that corresponded to each symbol according to the original code,” wrote the authors.

“This test, an index of information processing speed and working memory, has emerged as one of the most sensitive markers of cognitive impairment in MS,” they wrote.

A small sample size was one important limitation to this study. The authors also noted that their reliance on self-reports of cannabis use was not confirmed by urinary toxicology. Finally, cannabis users and nonusers differed slightly in their treatment regimens: More nonusers took disease-modifying treatments while more cannabis users took antidepressants. However, neither of these differences was significant. Furthermore, wrote the authors, “the relation between disease-modifying treatments and cognition remains equivocal, and data [suggest] that patients with MS taking antidepressants are not more impaired on tests such as the SDMT.”