Marijuana Use Not Associated With Residual Cognitive Decline Later In Life

London, United Kingdom: Cannabis use does not appear to have residual adverse effects of cognition or memory, according to trial data published last week in the American Journal of Epidemiology.

Researchers at the Kings College, School of Medicine in London investigated the prospective association between self-reported illicit drug use and cognitive functioning during the mid-adult years. A total of 8,992 participants who were surveyed at 42 years of age in the National Child Development Study (1999-2000) were included in the study.

Authors analyzed data on three cognitive functioning measures (memory index, executive functioning index, and overall cognitive index) when the participants were 50 years of age (2008-2009). Multivariable regression analyses were performed to estimate the association between different illicit drug use measures at 42 years of age and cognitive functioning at 50 years of age.

Investigators reported that those subjects who had used illegal drugs, primarily cannabis, as recently as in their 40s performed as well or slightly better on the tests than did their peers who had never used illicit substances.

The scientists concluded, "At the population level, it does not appear that current illicit drug use is associated with impaired cognitive functioning in early middle age. … The lack of association between current illegal drug use and cognitive functioning also appears to be congruent with previous evidence showing the absence of a long-term residual effect of illicit drug use on cognition."

For more information, please contact Paul Armentano, NORML Deputy Director, at: Full text of the study, "Is illicit drug use harmful to cognitive functioning in the mid-adult years? A cohort-based investigation," appears in the American Journal of Epidemiology. Additional information regarding cannabis use and cognitive function is available online from NORML at: