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 by an individual or small group? The quality of the marijuana could certainly have an effect on the results of the tests taken by the different groups. While the study contributes greatly to the research into the effects of marijuana on cognition, further studies should be done to compare the IQ scores of marijuana smokers to those who have never used marijuana.

Larsen, Dana. "Pot Makes You Smart!" Cannabis Culture. July 2002: 33.

The article "Pot Makes You Smart!" featured in Cannabis Culture Magazine was a cover of the study published in The Canadian Medical Association Journal. The author began by giving the many headlines about the study and pointing out that the headlines conflicted depending on where the article originated. The author goes on to tell that the study consisted of light users, heavy users, and non-users. Light users were those who smoked less than 5 joints a week and heavy users smoked an average of 33 joints a week. It also told how all participants in the study had been given IQ tests between the ages of nine and twelve and yet again later in life to see how their lifetime of marijuana use might have effected their IQ's. At the end of the article the results were listed that the non-users scores' stayed the same or increased slightly, the light users scores' increased by an average of five points more than the non-users, and that the heavy users scores' actually declined by about four points. In addition to the IQ score results the article also mentioned that after having abstained from marijuana for three months the differences between the groups' IQ levels disappeared proving there is no permanent harm to IQ scores.

The author did a decent job presenting the study except that she omitted the former users category (those who had not smoked regularly in at least three months) from the study. I'm not sure why the category was