Long-Term Cannabis Smoking Doesn't Impact Cognition, "Study"

Long-term use of cannabis does not lead to a decline in mental function, according to the results of a large-scale John Hopkins University study.

"There is no convincing evidence that [even] heavy long-term cannabis use impairs memory or other cognitive functions," said Dr. John P. Morgan of City University of New York (CUNY) Medical School. "During the past 30 years, researchers have found, at most, minor cognitive differences between chronic cannabis users and nonusers, and the results differ substantially from one study to another."

The  John Hopkins study examined cannabis's effects on cognition on 1,318 participants over a 15 year period. Researchers gave subjects specialized tests, called Mini-Mental State Examinations (MMSE), in 1981 and 1982. Subjects took follow-up MMSE tests 12 to 15 years later and scientists measured rates of cognitive decline among cannabis smokers and nonsmokers.

Researchers reported "no significant differences in cognitive decline between heavy users, light users, and nonusers of cannabis." They also found "no male-female differences in cognitive decline in relation to cannabis.

"These results ... seem to provide strong evidence of the absence of a long-term residual effect of cannabis use on cognition," they concluded.

The study is the first to investigate the long term effects of cannabis on cognition in a large epidemiological sample.

Researchers did conclude that cognition declines over long time periods in all age groups, but found this decline "closely associated with aging and educational level, [and] ... not ... associated with cannabis use."

The study appears in the American Journal of Epidemiology.

For more information, please contact John P. Morgan of CUNY Medical School @ (212) 650-8255 or Allen St. Pierre @ (202) 483-8751. To read an abstract of this study online, please visit: www.jhsph.edu/Publications/JEPI/may199/may1con.htm