THC & Cognitive Function

Ian Goddard (
Thu, 09 Dec 1999 23:43:24 -0500

In contrast to the tofu study suggesting tofu may cause brain atrophy, this recent epidemiological study found that cognitive decline in a large group of cannabis users over 12 years was not significantly different than nonusers, and concluded that the observed decline "does not appear to be associated with cannabis use." The fact that there were was no significant difference in cognitive decline between heavy users and light users also suggests no cannabis-induced decline.

American Journal Of Epidemiology, 1999 May 1;149(9):794-800

Cannabis use and cognitive decline
in persons under 65 years of age.

Lyketsos CG, Garrett E, Liang KY, Anthony JC

Department of Psychiatry and Behavioral Sciences, School of Medicine, The Johns Hopkins University, Baltimore, MD, USA.

The purpose of this study was to investigate possible adverse effects of cannabis use on cognitive decline after 12 years in persons under age 65 years. This was a follow-up study of a probability sample of the adult household residents of East Baltimore. The analyses included 1,318 participants in the Baltimore, Maryland, portion of the Epidemiologic Catchment Area study who completed the Mini-Mental State Examination (MMSE) during three study waves in 1981, 1982, and 1993-1996. Individual MMSE score differences between waves 2 and 3 were calculated for each study participant. After 12 years, study participants' scores declined a mean of 1.20 points on the MMSE (standard deviation 1.90), with 66% having scores that declined by at least one point. Significant numbers of scores declined by three points or more (15% of participants in the 18-29 age group). There were no significant differences in cognitive decline between heavy users, light users, and nonusers of cannabis. There were also no male-female differences in cognitive decline in relation to cannabis use. The authors conclude that over long time periods, in persons under age 65 years, cognitive decline occurs in all age groups. This decline is closely associated with aging and educational level but does not appear to be associated with cannabis use. &Dopt=b