Denver – Chinese and other Asians began ingesting cannabis 12,000 years ago. It was brought to North America for the first time by the Spanish in the 1500s, and Jamestown settlers introduced hemp a short time later.
But, it wasn’t until Ralph Mechoulam discovered THC in 1964 that researchers were given something to hang their hats on in the search for scarce research dollars. During its long and controversial history in the new world, marijuana has been studied in obscure ivy-covered ivory towers, a few hospitals and drug treatment sites, and there is general agreement that with the increasing legalization for both recreational and medical uses, much more research needs to be done to determine the long-term effects of cannabis use.
The five sessions devoted to the study of cannabis at the August convention of the American Psychological Association (APA) drew standing-room only convention goers interested to catching up on the latest research in marijuana use and treatment of those who have become addicted.
Yet, despite some interesting findings in the studies of marijuana, there is a consensus among researchers and others that the surface has hardly been scratched and that there is much to do and the full impact of the growing use of both legal and illegal cannabis is far from being nailed down. The latest figures show that 30 million Americans smoke marijuana, a significant increase in the last few years.
In a symposium titled “Trials, Tribulations, Possibilities – What to do About Cannabis?,” Ryan G. Vandrey, Ph.D., of the Johns Hopkins University School of Medicine, talked about studies on the effects of varying levels of THC on a number of participants over a nine-day period. Participants were given three doses of either 10, 25 or 50 milligrams of THC or a placebo.
The higher the dose the more paranoid, anxiety and dizzy the participants felt, with a few participants getting ill, Vandrey said. In another study he conducted in California and Washington on brownies containing an advertised average of 15 milligrams of THC, it was found most of the products were mislabeled, either containing more or less THC than noted on the packages.
Marcel O. Bonn-Miller, Ph.D., of the VA Palo Alto Health Care System, said his work with veterans suffering from PTSD showed that the trend was for them to become addicted to cannabis, suffering from withdrawal symptoms and sleep deprivation. Much of the work involving drug treatment requires intensive commitment and long-term therapy, he added.
On the prevention side, Walter A. Mason, Ph.D., of Boys Town National Research Institute for Child and Family Studies, said a study involving 8th grade students in five poor performing schools in Tacoma, Wash., revealed a high incidence of marijuana use. He said the sample studied was too small to draw any conclusions, but added that it was important to develop messages and other media to educate junior high students on the dangers of smoking marijuana.
In another symposium dealing with the effects of cannabis on cognition, Francesca M. Filbey, Ph.D., of the University of Texas at Dallas, said cannabis studies she has been involved in during the last 10 years shows there are lower IQs among long-term cannabis users, although more study is needed to see if there is a cause and effect.
Another study, this one by Jodi Gilman, Ph.D., of the Harvard Medical School, showed that marijuana users are more sensitive to fears of social exclusion and that the desire to avoid social rejection was higher than non-marijuana users.
“The cannabis users were more aware of being excluded and more susceptible to peer influences, which showed up on a number of computer-based exercises,” she said.
Catherine Stanger, Ph.D., of the Geisel School of Medicine at Dartmouth, noted that a study of 25 persons between 14 and 18 in Baltimore, showed significant loss of executive decision making ability among the mostly male participants who averaged of two marijuana cigarettes every day. In a three-month program, which involved an incentive of $370 if they completed the entire course, cognitive tasks improved as well as their working memory.
The students’ risk-taking improved and after 25 days of abstinence there was little or no effect on their executive functions, she said.
During a discussion period, Igor Grant, MD, of the University of California-San Diego, said “more is not known than is known” about the long-term effects of cannabis use. He questioned how reliable studies are that show there is no abnormality after 28 days of abstinence while similar data on alcoholics take six month to two years to determine such things. He added that there is significant incomplete data in most, if not all studies, looking at the results of smoking cannabis through adulthood and how that relates to IQ scores 20 years later.
Grant also said more emphasis needs to be placed on diversity and other factors that look at much larger populations from diverse cultures.
APA officials reported that about 11,000 attended the convention held in the Colorado Convention Center.