Addiction is the continued or compulsive use of a substance, despite negative and/or harmful consequences. Over the years, addiction has come to be re-defined to include behaviours, as well as substances, and the term is now used to describe significant problems with alcohol, nicotine, drugs, gambling, internet use, and sex.
The 'major' addictions, like alcoholism and drug abuse, stimulate significant amounts of research and are now largely well characterised, but others, like pathological gambling and internet addiction, are much less understood.
And then there is food. Food is a biological necessity, a distinction that makes it unlike any of the other substances or behaviours typically considered as addictive. It therefore also doesn't qualify when considering the typical conditions of abnormal dependence upon a substance – tolerance and withdrawal.
Binge eating a new diagnosis
At the same time, research has long found similarities between food intake and addiction. And just recently announced, the updated version of the Diagnostic and Statistical Manual of Mental Disorders, commonly called the DSM, will now formally include binge eating disorder as a new diagnosis.
Neuroimaging work has revealed that the same regions of the brain process the reinforcing effects of food and the consumption of drugs of abuse. The overlap of these neural circuits, however, does not necessarily mean that food is, or can be, addictive.
This lack of clarity in the scientific literature prompted the publication of this cohesive look at the support for and against the application of the addiction model to food. This Biological Psychiatry issue was led by guest editors Drs. Dana Small and Ralph DiLeone, at the Yale School of Medicine. Their goal was to bring together original research findings, systematic reviews and opinions of key leaders in the field to objectively represent the state of the field and both sides of the debate.
"While it is attractive to use the addiction framework to 'jump start' and guide our understanding of how neural circuits of reward and self-control might contribute to understanding overeating and the obesity epidemic, the price of adopting an inappropriate framework would be high," note Small and DiLeone. "For example, an inappropriate adaptation might steer research towards evaluating variables that have been shown to be critical for addiction at the expense of those that are unique to obesity and perhaps key to understanding overeating."
Papers in this issue cover the common and divergent neurobiological mechanisms and characteristics of food and substances of abuse. One provides rationale for adopting the food addiction model, arguing that food addiction exists and that although food is less powerful than addictive drugs, this does not diminish the compulsive nature or lack of control associated with binge eating. In contrast, another paper argues that the concept of food addiction is problematic and its links to drug addiction are overstated.
The brain and addiction
These juxtaposed papers are followed by reviews outlining the differences and similarities in brain reward circuitry, covering obesity, addiction, impulsivity, and self-control. The role that dopamine, a neurotransmitter critically involved in pleasure and reward, plays in food is also summarized.
Others cover the theme of neural adaptations, where new papers detail research findings on the changes observed in the brain following reward-driven feeding, reward and habit responding, and the effects of a high-fat diet. Another series of papers examine risk factors and susceptibility, including stress levels and how weight is related to an individual's degree of reward responding.
Binge eating disorder, the newest diagnosis within the eating disorder category of mental illnesses, is not left out. In fact, Small and DiLeone explain that the papers presented here provide a strong consensus, suggesting that binge eating may represent a sub-type of obesity most closely related to drug addiction.
Experts also comment on future directions for additional research and policy implications, considering how the verdict to adopt or reject the addiction framework will influence the national debate of how to address issues of diet, nutrition and obesity prevention.