by Rachel Harris
Many addictive drugs, such as nicotine, alcohol, and amphetamines, change the levels of dopamine in an area of the midbrain called the substantia nigra. In disrupting the dopamine systems in the brains, these drugs interrupt the brain’s quest for rewards and control of decisions. Recently, the obesity epidemic has catalyzed many psychologists to examine how food consumption acts on the brain in ways similar to substances more typically associated with addiction. Researchers at the National Institute on Drug Abuse have compared brain images of obese people and methamphetamine users. They have found that fewer dopamine receptors in both groups, when compared to a normal control group. Moreover, the signs of drug addiction: developing tolerance, withdrawal symptoms, and overwhelming involvement are also seen with food. [Editor's note: More on food "addiction" in this post on the hazards of delicious food. ] In addition, the absence of food is seen to cause withdrawal symptoms in rats. Although these results cannot be directly applied to humans, this study suggests that food might create powerful motivations to eat not only because the taste is rewarding, but also because eating reduces anxiety or stress.
In my editor mode on this site, I have actually been resisting putting up posts about “food addiction” but it has proven to be a popular notion. Let me explain why I think it is a mistake, despite the evidence Rachel Harris and Amiele Major have cited in their posts.
Drugs, like cocaine or methamphetamines work by taking advantage of brain systems that evolved for a very different purpose. They tap into the dopamine reward system, sending chemical message that says “that was good, do it again.” That is a problem if what you just did was use a drug, since it may lead to a cycle of escalation. But in tapping into this system, the drugs are like imposters. They deliver a message that should carry with it some advantage for survival or reproduction, but they really create a disadvantage.
Food, on the other hand, is the real thing. This is one of the stimuli that the dopamine reward system was surely evolved for. For most of our evolutionary history, and for most of the world’s population today, eating is a behavior that does carry an advantage for survival. It is only for those of us in overfed cultures with an abundance of fatty and sugary foods that there is a problem with that message.
So rather than likening our behaviors toward food to an addiction to drugs, the metaphor should be the other way around. Our behaviors toward addictive drugs are similar to our behaviors toward good food precisely because the drugs are hijacking the neural pathways that were intended for stimuli like food, that carry a survival value.
Comment by intro2psych — December 19, 2007 @ 11:25 pm
I recently read an article about ‘IAD’ (Internet Addiction Disorder). I at first thought it was a joke, but it turns out there are actually some psychologists who are doing research in this area and want to make IAD and official disorder! If we can actually become addicted to the internet, then where does it end? Can we be addicted to anything? We have all heard of addictions to shopping, television, video games, chocolate etc. However we do not think of these as actual disorders, such as alcohol or drug addiction. Apparently some of these activities do produce a similar effect in the brain as addictive substances . They give us an immediate dopamine rush, which we want more and more of. I decided to do some research to see if compulsive facebooking was really comparable to heroin addiction.
First of all addiction can be defined simply as “A habitual or compulsive involvement in an activity” . In this case the internet fits easily into this definition, but should it be an official disorder? Kimberley Young argues that is should. She has even written several books, Caught in the Net and Tangled in the Web about IAD and how to deal with it. This is a website about fighting the disorder, which also lists its symptoms and allows you to take a self-diagnosis test! There is, however, also a lot of criticism of the research done on IAD, from other psychologists, suggesting the mostly survey-based research is weak and inconclusive.
If we consider the two components of addiction, physiological and psychological , IAD seems to have mainly psychological symptoms, so it cannot logically be compared to other addiction disorders, with serious physiological withdrawal symptoms like various drug addictions, however some mainly psychological addiction disorders are considered official, Pathological Gambling for example, which is exactly what Young compares with IAD. I think actually making IAD an official disorder is a bit of a stretch but who knows…after all estimates suggest 5-10% of the U.S. population may have IAD already!
Comment by Marika Ison — December 26, 2007 @ 8:34 am
An attempt to construct single, rigid definition for food addiction (and perhaps addiction in general) is dangerously misleading.
In terms of food addiction specifically, nature of the problem must be considered. Obesity is not due to one simple cause. Some overweight people have problems with binge eating, others suffer from metabolic disorders, or may have thyroid problems, or genetic predispositions to obesity.
But the fact that not all cases of obesity are created equal is not the only difficulty in defining obesity as an addiction. Thomas Szasz, identifies a problem with classifying obesity as an addiction, calling addictiveness a “social” category (http://www.szasz.com/freeman21.html). From what I understand of his problem with labeling obesity as an addiction, it seems to me that he is correct in saying that social perceptions color our ideas of addiction; dependence on illegal drugs is an addiction, but some depend on legal prescribed drugs to fit the “medical norms of social behavior,” a dependence which may not be considered an “addiction” despite matching the signs of drug addiction. (Old paintings and other works of art seem to show that big used to be beautiful in past societies, but now that thin is in, the food is an addiction.)
The definition of addiction evolving from this article is that addiction is ostensibly manifested by the alleged lower number of dopamine receptors, which researcher Dr. Wang cautions “cannot determine if the brain changes in the obese individuals are a consequence or cause of obesity.” If this correlation is found to hold up after further testing, and even if it is shown to have something to do with causation, it still can be used as a research definition in a particular case at most.
It sounds nitpicky to get worked up over semantics, but poor semantics seems to be a growing problem in understanding medical issues. Some medical problems can be defined categorically: either you have typhoid fever or you do not. Even problems that can be subjected to such categorization can occur in different intensities (you have a mild case or a bad case of typhoid). Obesity does not lend itself to categorization; it seems to occur as a continuum, possibly partly because it does not stem from one simple cause. Because it is so hard to define, obesity is a subject that must be treated with greater maturity. Part of this maturity includes the realization there is no single easy definition with which to label as complex a concept as addiction.
http://www.szasz.com/freeman21.html
Comment by IntroToPsychology — February 28, 2008 @ 12:13 pm
While the title of “This is Your Brain on Food” implies a connection between compulsive eating and drug addiction, the article does point out several differences between the two. For example, while chronic drug use disrupts part of the frontal cortex involved in inhibiting behaviors, chronic compulsive eating is not associated with such a disruption. In a study in which subjects were made to feel full using an implantable gastric stimulator, subjects still felt and responded to a powerful motivation to eat, indicating that over-eating seems to occur because the drive for food is more powerful than existing inhibitory control and thereby overrides the control (as opposed to occurring because of a lack of effective inhibitory control).
The obese subjects of Dr. Wang’s study had fewer D2 dopamine receptors than the control group (a negative correlation). Interestingly, within the obese group itself there was a negative correlation between BMI and number of receptors, while in the control group no such correlation was found. This may suggest that there is a “threshold weight” (or “threshold BMI”) specific to each individual that represents a quantifiable biological line between obese and not obese, an idea which may present an area of further study. The article explained the role of dopamine in eating and response but did not explain why research was conducted examining the D2 class of dopamine receptors in particular out of the many existing classes (D1 through D5, and potentially D6 and D7). This may be an area requiring further explanation or more study.
Reference
Ozelli, K. L. (2007, September). This is Your Brain on Food (Extended Version).
Scientific American. 1-3. Retrieved 19 Feb. 2008 from http://www.sciam.com/ article.cfm?id=this-is-your-brain-on-food-extended&page=1.
Comment by IntroToPsych — March 7, 2008 @ 4:02 pm