Can stress and social standing influence brain chemistry and vulnerability to addiction?
That intriguing possibility is supported by a study in monkeys conducted by researchers at Wake Forest University School of Medicine. The researchers used PET to measure changes in levels of dopamine D2 receptors in macaques that were placed together after being housed separately.
Receptor levels rose in monkeys that established a dominance position in the social hierarchy, but not in subordinate animals, the researchers reported in the January 2002 issue of Nature Neuroscience. The subordinate monkeys also self-injected cocaine more frequently than did the dominant animals, indicating that they were more vulnerable to the reinforcing aspects of cocaine.
While this kind of study has not been conducted in humans, the genetics and neurobiology of social behavior is “extraordinarily important,” says Nora Volkow, M.D., director of the National Institute on Drug Abuse “If you have all of the genes that make you addicted and you are in an extremely protected environment, you will never become addicted.”
On the other hand, early exposure to drugs like nicotine may cause long-lasting neurochemical changes—particularly in the still-developing adolescent brain.
Children who start smoking at age 12 or 13, for example, have a higher risk of developing an anxiety disorder than non-smokers. It is not known whether nicotine exposure triggered the disorder, or whether the children started smoking to relieve pre-existing—and undiagnosed—anxiety.
Either possibility, however, can lead to nicotine addiction and to the well-known health consequences of smoking. By masking symptoms, smoking also can delay diagnosis and appropriate treatment of the anxiety.
“It follows that one of your prevention strategies against mental illness may be to minimize the chances of kids getting exposed to drugs,” Volkow says. “If we want to (prevent) drug addiction and aberrant behavior and decrease the risks for some mental diseases, we need to do strategies that will compensate and intervene at the community level or at the parent or the school level.
“We need to develop the interventions, of course, but… imaging offers you the capacity to evaluate the effectiveness of your intervention.”