Stressors such as poverty, parental neglect, social stigma and physical or sexual abuse can increase a person’s vulnerability to drugs, and that has implications for the treatment of addicted individuals, particularly juveniles, who are imprisoned, the director of the National Institute on Drug Abuse (NIDA) told a meeting at AAAS.
Dr. Nora Volkow, the NIDA director, said putting addicts in jail can increase their stress levels and, if they do not have access to treatment, could worsen their outcomes. While many cultures still regard addiction as a moral weakness, Vokow said, it is important to treat it as a disease and “change the model of criminalization of the addicted individual into one of treatment.”
Dr. Nora Volkow | Photograph by Michael J. Colella, colellaphoto.com/© AAAS
Volkow, while stressing that she does not advocate the legalization of marijuana or other illicit drugs, said science has been describing in some detail the complex mix of genetics, development, environment, and neurochemistry that can lead to addiction. “We have to bring drug addiction into the health care system,” Volkow said, rather than just leaving it to the criminal justice system. “Most of the physicians don’t even screen for substance abuse disorders.”
Volkow spoke at the 2011 Summer Leadership Institute of the Society for the Advancement of Chicanos and Native Americans in Science (SACNAS), an event co-organized by AAAS Education and Human Resources and held in the AAAS building 25-29 July. The annual institute seeks to foster leadership skills in 30 selected doctoral-level scientists from underrepresented groups. The program includes group exercises, talks by role models, mentoring, and networking opportunities.
Volkow told the institute participants that while addicts still must take responsibility for their actions, “putting someone in jail for being an addict does not solve anyone’s problem.” The rate of re-incarceration and relapse is extraordinarily high, she said, and “it is much more expensive to put someone in jail or prison than to treat them.”
The issue can be particularly acute for minorities, Volkow said. They are more likely than others to be given prison sentences for drug-related offenses, she said, and also are more likely to have already suffered social stigma. Imprisonment compounds the problems, she said, since “there is nothing more stigmatizing” than being sent to jail.
Volkow, who had been a leading addiction researcher at Brookhaven National Laboratory on Long Island, New York, before taking the helm at NIDA in 2003, said she quickly learned in Washington that science does not necessarily lead to policy changes. She told participants in the SACNAS institute that it is important to marshal evidence that will be impossible for policy-makers to ignore and “let the data speak for itself.”
On that score, Volkow said, recent studies have been providing solid insights into the addicted brain and possible avenues of treatment.
Imaging studies of glucose metabolism in the brain have shown that the frontal cortex?the center for cognitive control?can be affected by repeated administration of drugs. Studies also have shown that connections between the frontal cortex and the limbic system—which controls a variety of functions, including emotion—are not fully formed until the early 20s. Developmentally, adolescents are more vulnerable to addiction because their brains have not fully matured, Volkow said.
But drug addiction is not just a function of repeated exposure to a particular drug during a time of developmental plasticity, Volkow said. Genetics plays an important role. If you have parents who have been addicted to alcohol or drugs, she said, you are likely to be more vulnerable to addictive behaviors. Environmental factors—including stressors such as poverty or social stigma—can reinforce an underlying genetic susceptibility.
“We now have the tools to see why social stressors make the brain more vulnerable,” Volkow said. Researchers have started to identify the biochemical pathways that are involved. In animal studies, including with non-human primates, researchers have begun to evaluate how social stress can affect the brain in ways that make it more vulnerable to drug abuse.
In imaging studies, researchers consistently have found lower levels of a protein called the “dopamine D2 receptor” in brains of persons addicted to cocaine, amphetamines, alcohol, heroin, and nicotine. Dopamine is the primary neurotransmitter involved in the reward pathways in the brain. Studies in Volkow’s lab at Brookhaven and elsewhere suggest that a deficiency in dopamine D2 receptors may make people, and animals, less able to experience ordinary pleasures and more vulnerable to alcoholism and drug abuse. Volkow said a D2 receptor deficiency increases the vulnerability to compulsive drug taking and loss of control.
Using mice, researchers also have explored a possible genetic intervention in the dopamine pathway to counteract compulsive alcohol or cocaine intake. Scientists used an adenovirus vector to carry the gene for the D2 receptor into a key reward region in the brain called the nucleus accumbens. They showed that increasing D2 receptors by 50% resulted in a dramatic reduction in alcohol or cocaine intake by the animals. The effect is transitory since the hitch-hiking D2 receptor genes are not incorporated permanently into the animal’s DNA. But the results are promising, and Volkow said that, at least in rodents, alcohol or cocaine intake can be controlled by modifying the genes that regulate biochemical signals via the dopamine D2 receptors.
In studies of non-human primates, researchers at Wake Forest University showed that a social stressor can change the number of D2 receptors in the brain. The scientists studied animals reared in isolation and found that when they were moved into a more social group setting, the D2 receptor levels increased in the dominant animals. Those who were subordinate in the group—under substantial stress—had fewer receptors and were much more likely to self-administer cocaine than the dominant animals with high D2 receptors levels.
While animal studies suggest that manipulation of both genes and environment might provide avenues to lessen addictive behavior, it is unclear whether genetic manipulation is either feasible or desirable in humans.
But Volkow said addiction can be treated, and there are several interventions that can work, including self-help groups, mental health therapy, and outpatient and inpatient rehabilitation. However, these are not being used as widely as they could be, she said. In 2007, according to Volkow, an estimated 22.3 million Americans were dependent on or abused alcohol or illicit drugs. Only 3.9 million of them (17%) had received some sort of treatment in the previous 12 months.
Successful treatment can have an impact on neurobiology. One study found a partial recovery of normal dopamine transporters in methamphetamine users who had been able to abstain from the drug for at least 14 months.
It also is possible to buffer the impact of adverse environments as a way to help prevent addiction, Volkow said, not least by trying to reduce social stressors on vulnerable populations. She noted that humans do not live in just one hierarchical system like the apes in the Wake Forest study. A person may have a subordinate, stressful job that could increase vulnerability to addiction, she said, but he or she might also be a leader in a church community or other activity that provides a buffer to such stress. Giving children opportunities to succeed in school, sports, the community and the family, she said, “is the single best intervention to prevent drug abuse.”
It is important to initiate prevention strategies in childhood and in the adolescent years when the developing brain is most vulnerable to the reinforcing impact of drugs and alcohol, Volkow said. Adolescents can become addicted more quickly than adults, she said, and the addiction can be harder to treat. “It’s like a memory that is much more indelible,” she said. In fact, the same molecular mechanisms that are involved in learning and memory also come into play in addiction. In the case of adolescents, Volkow said, it is essential to address the addiction as soon as possible.
Volkow, who was born in Mexico and earned her medical degree at the National University of Mexico in Mexico City, was warmly received by the SACNAS group. She told the institute participants that intelligence and vision are important attributes of leadership, but more important are passion and compassion. “If you don’t have passion for what you do,” Volkow said, “it’s very difficult to maintain the level of effort” that a leadership position requires and to translate what you do to others. And compassion sends a message that “you are doing something that ultimately will transcend you and will help others.”
Learn more about the Society for the Advancement of Chicanos and Native Americans in Science (SACNAS) and its Summer Leadership Institute.