Sunday, March 4, 2007

Drug Abuse: Are Brains Predisposed to the Problem?

According to BBC News, government figures estimate that in Britain “up to 500,000 people are currently addicted to Class A drugs such as cocaine, heroin, and amphetamines.” In addition, drug abuse is prominent with reported use at about 53% for adolescents in 12th grade, according to the 2003 Teen Drug Abuse statistics, which also states that as many as 30% of youths 14 years old were misusing drugs. An important question regarding addiction has always surrounded the origin of brain differences observed in drug users, displayed to the left, and whether they resulted from their individual brain makeup or from previous drug use. These differences are physical in nature, one of which includes a scarcity of dopamine receptors in one area of the brain. The findings from one study provide great insight while indicating the possible answer. This study conducted by Dr. Jeff Dalley of the University of Cambridge and published March 2 in the journal Science claims that some individuals may be predisposed to the effects of cocaine on the brain, making them more likely to try the drug and become addicted. It is widely recognized that drug addiction is associated with risk taking, sensation seeking, and impulsivity, according to Miranda Hitti of WebMD Medical News, and Dalley's experiment sought to determine the role of dopamine on impulsivity and drug addiction.

Dr. Dalley examined rats without any previous exposure to drugs, and tested them on impulsivity. The rats were confined in a cage as a light was randomly and briefly illuminated in different spots throughout the cage. While the rats that ran towards the light were rewarded with food, those who “impulsively” ran to the wrong spot were not rewarded with food. These impulsive rats demonstrated two interesting findings. They were not only more likely to continuously and obsessively self-administrate cocaine through an IV tube than the less impulsive rats, but they also were more likely to possess fewer dopamine receptors, pictured to the right, prior to cocaine exposure than the less impulsive rats. This was detected by a PET scan. Interestingly, human addicts also have a scarcity of dopamine receptors in the same area of the brain, the nucleus accumbens, which is involved with motivation and behavior. According to an article from Medline Plus, Dr. Nora Volkow, director of the U.S. National Institute on Drug Abuse believes it is well-known that low levels of dopamine receptors in the nucleus accumbens, shown below, are linked to addiction, thus encouraging the use of drugs.

This is a very significant discovery because it suggests that an individual’s natural brain chemistry is setting him or her up for drug abuse, and it is not just the addictive drug itself. Knowing that a shortage of dopamine receptors appears before drug exposure provides additional knowledge on the causes of addictions, and what can potentially be done to combat them. While this is promising, it is still necessary to be skeptical that brain configuration is the only factor driving drug abuse. Although impulsivity seems to be playing a large role in compulsive drug disorders, it seems only reasonable that a multidisciplinary aproach be essential to an intervention since a variety of factors for substance abuse must be taken into account. Clearly it is more complicated than just reducing impulsivity and risk-taking behaviors. In the BBC article, Martin Barnes of DrugScope plainly agrees that “[t]he reasons why any particular individual may start using drugs and become a problem drug user are far more complex than just genetic make-up.” While it should not be disregarded that this genetic trait may produce vulnerability to addiction problems, ultimately, there are many reasons why one may initiate drug use. Therefore it is imperative to keep an open mind regarding the causes of addictions and what can be done to prevent and treat them. In doing so, valuable therapeutic strategies will not be overlooked so that with additional time and research, an effective treatment procedure will hopefully reveal its success.

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