T. Evarts
The controversy about whether addiction is a disease or a choice has been heavily debated. Addiction is characterized by changes in brain systems that mediate the experience and anticipation of reward systems responsible for perception and memory. The data show that the addict’s brain is functionally different from the non-user; however, changes in brain function are caused by changes in brain structure. Because addiction alters brain structure causing change in brain function, it is a disease.
All addictive substances have the same effects on a single pathway in the brain, the mesolimbic reward system, which extends to the orbitofrontal cortex. Studies in laboratory animals have shown that damage to this part of the brain prevented the animals from stopping a learned behavior; this is comparable to an addict being unable to stop using a drug. The orbitofrontal cortex is activated when a person is expecting a conditioned stimulus, or a learned behavior. Activation of this system causes the compulsive behavior of an addict, and the motivation of using the drug even when it is no longer pleasurable. The figure adapted from Volkow et al. shows the brain scans of a high craver (addict) and a low craver (non-user) when a placebo drug and a psycho- stimulant drug (methylphenidate (MP)) were administered. MP significantly increased the metabolism in the right orbitofrontal cortex which induced high levels of craving in addicts, but not in non-users. The difference in metabolic activity between the subjects is indicative of the change in brain function an addict experiences. One could argue that the increased metabolic activity is an effect of the drug rather than a cause of addiction. If the drug is what causes the metabolic activity then the data would show higher metabolic activity in the non-user’s brain scan when methylphenidate is administered, however there is more metabolic activity in the non- user’s brain when the placebo was given. This is significant because it shows the difference between an addict’s and a non-user’s brain function.
What makes addiction a disease rather than a choice is the change in brain function. The difference in the metabolic activity shown in the data is representative of the functional difference between an addict’s brain and non-user’s brain.. Understanding addiction begins with realizing the brain is the root of the problem, so the brain should be the root of the solution as well. The acceptance of addiction as a disease is the first step in gaining control over drug abuse.
*Volkow et al., Cerebral Cortex, Volume 10, Number 3, 2000
