Labs at UCSD and around
are investigating the medicinal value and addictive qualities of cannabis, the
drug that, according to the United Nations Office on Drugs and Crime, is used
by approximately 162 million people each year.
Like many other recreational drugs, marijuana binds to the
brain’s receptors. Receptors are similar to keyholes, which release an effect
throughout the body when the correct link is made. However, unlike many of the
body’s other compounds, the brain has receptors that respond specifically to
chemicals found in marijuana, called cannabinoid receptors. These receptors
trigger physical rewards in the body during exercise, in what UCSD School of
Medicine professor of anesthesiology Dr. Mark Wallace likens to “the runner’s
high.”
The most common cannabinoid in marijuana is
tetrahydrocannabinol, or THC. According to Wallace, there are over 450
compounds within the plant that contribute to marijuana’s effects.
Wallace’s most recent study on cannabinoids involved 15
healthy individuals who inhaled marijuana and endured pain from a forearm
injection of capsaicin, the compound that produces the spicy sensation in chili
peppers.
Wallace found that if capsaicin was injected 45 minutes
after a subject smoked marijuana, there was a significant decrease in pain.
However, if capsaicin was administered five minutes after the subject smoked,
there was no significant decrease in pain. In addition, Wallace found that task
performance and motor skills in his study were not significantly impaired with
a dose of 4 percent THC marijuana.
“This study was conducted to put the debated pain-relieving
quality of cannabis to the test,” Wallace said. “We were shown that there is a
potential benefit in using cannabis moderately to treat patients with chronic
pain.”
Wallace’s study was funded by SB 847, a bill signed into
effect by former Gov. Gray Davis in 1999. The legislation allowed the
of
California Medical Marijuana Research Program. With this bill, as well as the
1996 State Proposition 215, the Center for Medical Cannabis Research was
established. Based in
affiliated with UCSD, the center gathers researchers to answer the ultimate
question involving marijuana — is it genuinely therapeutic and effective enough
for medicinal use?
“The ultimate goal for the CMCR is to test the safety and
efficacy of using cannabis and its compounds in medical treatment,” CMCR
representative Heather Bentley said. “This goal holds particularly true in
situations where there are no other solutions for patients who suffer from
chronic pain and or illness.”
Bentley said cancer, AIDS, obsessive-compulsive disorder,
diabetes, multiple-sclerosis and depression have all been medically treated
with the use of marijuana with some success.
While UCSD heads many cannabis experiments, it receives all
research marijuana from one government-funded source — the University of
Mississippi — which is governed by the National Institute on Drug Abuse, the
sole American contractor that has been growing legal marijuana since 1974.
At the Scripps Research Institute, NIDA is supplying another
project with drastically different goals. SRI Professor Barbara Mason is
heading a study that will look at addiction as a reason for constant marijuana
relapses.
Participants in Mason’s study are required to be regular
marijuana users and are paid to not smoke. They are given a medication which
abruptly blocks cannabinoid receptors, creating a full-scale withdrawal from
marijuana for day. This allows Mason and her colleagues to study marijuana
withdrawal within a short period of time, whereas natural withdrawal usually
lasts for months.
“Our study focuses on abuse and dependence on cannabis and
how it affects higher cognitive functioning, like reasoning, decision making
and problem solving,” Mason said. “We are trying to characterize marijuana
withdrawal.”
Mason said one of the most prevalent symptoms of marijuana
withdrawal is sleep disturbances, characterized by strange dreams and
interruptions that can last months after a user quits smoking. Other symptoms
include “violent outbursts,” such as aggressive behavior, anxiety attacks and
difficulty concentrating.
UCSD assistant professor of psychiatry Dr. Susan Tapert will
create magnetic resonance images of the brains of participants involved once
the study moves past its initial stages. The participants include some of
UCSD’s own students.
Tapert is particularly interested in how cannabis use
affects long-term development of the brain in adolescents and young adults.
“This matter is important to me because marijuana is so
widely used,” Tapert said. “About 5 percent of high school seniors report using
marijuana daily. It is import to understand its neurological effects, so that
young adults are rightfully informed about the effects of marijuana use.”
According to Mason, despite marijuana’s widespread use, its
effects on the body and mind are hardly understood. Because marijuana’s
long-term effects are still unknown, researchers like Tapert are focusing their
attention on teens and young adults, like undergraduates, whose learning
abilities could be affected by the substance.
“Like with any substance, overuse can bring undesired
results,” Wallace said. “In the future, marijuana’s place in medicine will
hopefully be understood, as well its adverse effects on the mind and body.”
