The truth behind addiction
Studies prove that stress makes people much more likely to search for solace in drugs or comfort food
s a psychiatrist I have yet to meet a patient who enjoys being addicted to drugs or compulsively overeating. Why would anyone continue to use recreational drugs despite the medical consequences and social condemnation? What makes someone eat more and more in the face of poor health?
One answer is that modern humans have designed the perfect environment to create both of these addictions. No one will be shocked to learn that stress makes people more likely to search for solace in drugs or food (it’s called “comfort food” for a reason). Yet, the myth has persisted that addiction is either a moral failure or a hard-wired behaviour — that addicts are either completely in command or literally out of their minds. Now we have a body of research that makes the connection between stress and addiction definitive. More surprising, it shows that we can change the path to addiction by changing our environment.
Neuroscientists have found that food and recreational drugs have a common target in the “reward circuit” of the brain, and that the brains of humans and other animals who are stressed undergo biological changes that can make them more susceptible to addiction.
In a 2010 study, Diana Martinez and colleagues at Columbia scanned the brains of a group of healthy controls and found that lower social status and a lower degree of perceived social support — both presumed to be proxies for stress — were correlated with fewer dopamine receptors, called D2s, in the brain’s reward circuit. All rewards — sex, food, money and drugs — cause a release of dopamine, which conveys a sense of pleasure and tells the brain something like: “This is an important experience. Don’t forget it!” The reward circuit evolved to help us survive by driving us to locate food or sex in our environment. Today, the more D2 receptors you have, the higher your natural level of stimulation and pleasure — and the less likely you are to seek out recreational drugs or comfort food to compensate.
Drug exposure also contributes to a loss of selfcontrol. Volkow found that low D2 was linked with lower activity in the prefrontal cortex, which would impair one’s ability to think critically and exercise restraint.
Reward circuit
The same neuroscience helps us understand compulsive overeating. Food, like drugs, stimulates the brain’s reward circuit. Chronic exposure to high-fat and sugary foods is similarly linked with lower D2 levels, and people with lower D2 levels are also more likely to crave such foods. It’s a vicious cycle in which more exposure begets more craving. Volkow and colleagues showed that morbidly obese individuals had reductions in their D2 receptors and that the reduction was proportional to their body mass index.
At this point you may be wondering: What controls the reward circuit in the first place? Some of it is genetic. We know that certain gene variations elevate the risk of addiction to various drugs. But studies of monkeys suggest that our environment can trump genetics and rewire the brain. The good news is that while we can’t change our genetics, we can change our environment.
Contemporary humans did not experience a sudden collapse in self-control. What happened is that cheap, calorie-dense foods that are highly rewarding to your brain are now ubiquitous. The processed food industry has transformed our food into a quasi-drug, while the drug industry has synthesised ever more powerful drugs that have been diverted for recreational use. Finally, the advertising industry may play a role. Volkow says that she and her colleagues are now “testing how the brain responds to subliminal messages” about food and drugs. Her hypothesis is that drug-addicted and obese individuals are more susceptible to such messages.
Fortunately, our brains are remarkably sensitive to experience. Although it’s far easier said than done, just limiting exposure to high-calorie foods and recreational drugs would naturally reset our brains to find pleasure in healthier foods and life without drugs.
In the meantime it’s worth remembering that we can’t control our genes or the misfortunes that befall us, much less their impact on our brains. Even the most self-disciplined can fall prey to a food or drug addiction under the right mix of adversity and stress.
Richard A. Friedman is a professor of Clinical Psychiatry and the director of the psychopharmacology clinic at the Weill Cornell Medical College, and a contributing opinion writer.