The Effects of Marijuana on Cognition

A discussion is taking place across the globe as to whether or not marijuana use has a negative effect on the mind and body of its users. This discussion has many participants with varying views on the issue. Some think marijuana use, while very harmful to your lungs, has no negative effect on the mind. Others see it as harmful to both the mind and the body. Still a select few see marijuana as a medicine. Marijuana and its effects have intrigued many for centuries. Its users have their own culture spreading across the globe. Over the years marijuana has acquired many different names such as pot, cannabis, weed, herb, green, ganja, smoke, dope, reefer, mary jane, and of course lets not forget the 60's and 70's grass. This culture of marijuana smokers is so large that several magazines in publication have devoted their ink to its use and its legalization. Also, in the medical community, studies have been done to investigate its effects.

I came across an article in a popular magazine entitled "Pot Makes You Smart!" Upon reading the title alone I was intrigued and had to read further. The article was an interpretation of a study done into the effects of marijuana on intelligence quotient (IQ). I was so enthralled that I had to find the original study to see exactly how the research was conducted in order to compare the actual results of the study compared with those printed within the magazine. I found an abstract of the study on the web at The Canadian Medical Association Journal, site. To further investigate marijuana's effects on cognition I read a chapter from the book entitled Marijuana Myths, Marijuana Facts: a Review of the Scientific Evidence, by Lynn Zimmer, Ph.D. and John P. Morgan, M.D.

"Current and Former Marijuana Use: Preliminary Findings of a Longitudinal Study of Effects on IQ in Young Adults." eCMAJ-JAMC 20 Mar. 2003. Abstract.

http://www.cmaj.ca/cgi/content/abstact/166/7/887?maxtoshow=&HITS=10&hits=10&R 2 Apr. 2002.

In searching for studies into the effects of marijuana, The Canadian Medical Association Journal site was quite helpful. The site included a study done to determine any cognitive effects of marijuana. The study is titled "Current and former marijuana use: preliminary findings of a longitudinal study of effects on intelligence quotient (IQ) in young adults." Professors Peter Fried, Barbara Watkinson, Deborah James, and Robert Gray from the Department of Psychology at Carleton University in Ottawa, Ontario, organized the study. In an attempt to assess marijuana's impact on IQ the organizers of the study used data of seventy 17-20 year-olds. Urinalysis and self-reporting was used to ensure marijuana use. These participants had been followed since birth and were given IQ exams around the age of 9-12 years old, before any marijuana use. Then around the ages of 17-20, these same participants were given another IQ exam after the initiation of regular marijuana use. Differences in scores were calculated by subtracting the score at 9-12 from the scores at 17-20. Then by separating the participants into groups like current heavy users (about 5 joints per week), current light users (less than 5 joints per week), former users (those who had not smoke regularly in the past 3 months), and current non-users (those who had never smoked more than once a week and had not smoked in the past two weeks), differences in scores were examined to determine if there were any affects on IQ.The Results of the study showed a decline of about 4.1 points in current heavy smokers as compared to an increase of about 5.8 points in current light users, 3.5 points in former users, and 2.6 in non-users. According to the study, marijuana only had negative effects in the heavy user's category and a positive effect in all other categories.

The study covered in this article, though organized by professors at C.U., seems to have a flaw. The group that was studied consisted of current heavy users (at least 5 joints a week), current light users (less than 5 joints per week), former users (who had not smoked regularly for 3 months), and non-users (who never smoked more than once a week and had not smoked in the past 2 weeks). The problem is not with how the group was split, but with how former users and non-users were classified. A former user should be classified as one who used to smoke but has not in the past year or two, and a non-user should be classified as one who has not and does not smoke marijuana. Without this group of actual non-users it is impossible to obtain the proper data needed to compare with the data of the user groups. One other minor detail is that the article never mentions the quality of the marijuana used in the study. Was it government grown marijuana, which is of the highest grade or was it low-grade marijuana grown