Tuesday, April 6, 2010

Impulsivity and Addiction

The perils of a hypersensitive dopamine system.

The brooding, antisocial loner, the one with impulse control problems, a penchant for risk-taking, and a cigarette dangling from his lip, is a recognizable archetype in popular culture. From Marlon Brando to Bruce Lee, these flawed heroes are perhaps the ones with restless brain chemicals; the ones who never felt good and never knew why (“What are you rebelling against?” “What’ve you got?”).

This post was chosen as an Editor's Selection for ResearchBlogging.orgA recent study at Vanderbilt University, published in Nature Neuroscience, used PET scans and fMRI imaging to suggest that impulsivity and other “antisocial” traits “predicted nucleus accumbens dopamine release and reward anticipation-related activity in response to pharmacological and monetary reinforcers, respectively.”

In other words, the Vanderbilt researchers maintained that so-called “psychopathic traits” like impulsivity and risk taking are linked to addiction and gambling by means of an overly active dopamine system. PET scans of dopamine responses to a low dose of amphetamine showed that “individuals who scored high on a personality assessment that teases out traits like egocentricity, manipulating others, and risk taking had a hypersensitive dopamine response system,” according to a press release from the National Institute on Drug Abuse (NIDA), which funded the study.

Putting a different spin on the matter, NIDA director Nora Volkow said: “By linking traits that suggest impulsivity and the potential for antisocial behavior to an overreactive dopamine system, this study helps explain why aggression may be as rewarding for some people as drugs are for others.”

Lead author Joshua Buckholtz of Vanderbilt said that “the amount of dopamine released was up to four times higher in people with high levels of these traits, compared to those who scored lower on the personality profile.  Buckholtz suggested that a pattern of exaggerated dopamine responses “could develop into psychopathic personality disorder.”

Dr. Robert Cloninger, a prominent addiction researcher, has asserted in the past that children who show a high propensity for risk-taking, along with impulsivity, or “novelty-seeking,” are more likely to develop alcoholism and other addictions later in life.

And, in interviews with the late psychologist Henri Begleiter for my book on addiction science, Begleiter insisted that addicts were stuck with a package of symptoms he called behavioral dysregulation. “Disinhibition, impulsivity, trouble fitting into society—you have certain behavioral disorders in kids who later develop into alcoholics and drug addicts,” he said. The behavior itself doesn’t cause the addiction. The dysregulated behavior is a symptom of the addiction.

“When you talk to these people, as I have,” Begleiter said, “you see that the one thing they pretty much all report is that, under the influence of the drug, they feel much more normal. It normalizes their central nervous systems. Initially, what they have is a need to experience a normal life.”

So, it wasn’t ducktails, pool halls, tattoos, casual sex, or lack of parental involvement that caused addiction to alcohol and cigarettes and pot, and maybe cocaine and speed and heroin. It wasn’t just the “bad kids.” Irrational anger, impulsive decisions, certain compulsive behaviors like gambling—these behaviors were symptoms of the same group of related disorders that included drug and alcohol addiction, and which involved specific chemicals and areas of the brain related to reward, motivation, and memory.

The trait of impulsivity is a possible marker for addiction that may help explain why it is usually impossible to persuade addicts to give up their drugs by sheer force of logic—by arguing that the drugs will eventually ruin their health or kill them. “They tell me it’ll kill me,” sang Dave Van Ronk, “but they don’t say when.”

Consider the always-instructive case of cigarette smoking. In 1964, the Surgeon General’s Report on Smoking and Health laid out the case for the long-term ill effects of nicotine quite effectively—and millions of people quit smoking. A stubborn minority did not, and many of them still have not. Are they simply being hedonistic and irresponsible? Or are the long-term negative consequences, so dramatically clear to others, simply not capable of influencing their thinking to the same degree? Biochemical abnormalities similar to those predisposing certain people to addiction may also prevent them from comprehending the long-term results of their behavior.

Buckholtz, J., Treadway, M., Cowan, R., Woodward, N., Benning, S., Li, R., Ansari, M., Baldwin, R., Schwartzman, A., Shelby, E., Smith, C., Cole, D., Kessler, R., & Zald, D. (2010). Mesolimbic dopamine reward system hypersensitivity in individuals with psychopathic traits Nature Neuroscience, 13 (4), 419-421 DOI: 10.1038/nn.2510

Graphics Credit: http://www.nature.com/neuro/journal/

1 comment:

Frank said...

Was wondering if you had reviewed a bit more recent cognitive study out of John Hopkins that highlighted a causal link between visual stimuli and reward related objects and experiences?
Absolutely love the blog. Thank ever so much for all you contribute.

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