NicVAX was evaluated in a recent study in the American Journal of Psychiatry, in a small cohort of 11 smokers who smoked an average of 19 cigarettes per day, smoked for an average of 10 years, thereby meeting criteria for nicotine dependence.

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"If you had a smoker compared to a nonsmoker and were able to do imaging study of the brain, the smoker would have billions more of the receptors in areas of the brain that have to do with pleasure and reward, " says Richard Hurt, an internist who heads the Mayo Clinic's Nicotine Dependence Center.

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But psychiatry as a field has been skeptical of the idea of people being addicted to behaviors, because there is not proof that a bad habit is the same kind of biological issue as a dependence on alcohol, nicotine, or heroin.

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