Drug dependence differs from drug abuse in three ways. First, drug dependence consists of clearly measurable periods of tolerance and withdrawal, whereas drug abuse sets the occasion for tolerance and withdrawal. Abuse means there exist early warning signs of life impairment predictive of physical and psychological dependence. Adults arrested for driving under the influence of alcohol, for instance, often face fears that their uncontrolled drinking may result in fatal vehicular accidents. Second, drug-dependent users show marked cognitive, behavioral, and psychomotor retardation in their daily activities. Personal history was not associated with the students' willingness to treat, but men were less willing to treat. Drawing strength from the randomized reinforcer experimental design nested within this survey approach, the study evidence suggests potential nonparticipation bias in standard surveys on this topic.