In this context, one sentence in the editorial concerned me: "A modern conceptualization of addiction is that it acts as a chronic disease produced by thousands of exposures to drugs." This sentence seems to imply that repeated exposure to drugs is a sufficient condition for developing drug addiction and that thousands of exposures are necessary for an addictive pattern of drug use to develop. I believe that neither of these implications accords with our experience. Repeated exposure to drugs typically produces neuroadaptation, which can manifest as tolerance, withdrawal, or both. While neuroadaptation can contribute to maintaining or increasing drug use, most investigators agree that neither tolerance nor withdrawal is necessary or sufficient for the development (or the diagnosis) of drug addiction. Moreover, an explanation of addiction that depends on repeated exposure cannot account for individual differences in susceptibility to addiction: some individuals who are repeatedly exposed to alcohol or other drugs will develop addictive patterns of substance use, while others with similar exposure will not. That a biopsychological vulnerability to developing addiction exists before the onset of substance use is indicated also by findings in longitudinal and archival studies that childhood temperamental disturbances—including high emotionality, low soothability, and impulsiveness—are associated with later development of alcoholism or drug addiction.