cate that some people who experiment with marijuana may be genetically predisposed to becoming regular users. Whether a person ever tries marijuana, however, appears to be most strongly influenced by one 's family and social environment.

Although marijuana seems to pose an increased risk of abuse for some people, it is generally considered to be only mildly addictive. Compared with users of several other addicting substances, few people who use marijuana become dependent on it (see Figure 3.2). Thus, while many more people try—and use—marijuana than other illicit drugs such as cocaine or heroin, marijuana abuse cases are relatively rare. Two large-scale surveys—the National Comorbidity Survey²⁴ and the Epidemiological Catchment Area Program²⁵—have found that about 5 percent of the U.S. population has been dependent on marijuana at some

FIGURE 3.2 Prevalence of drug use and dependence in the general population. The higher estimates for marijuana use shown here compared to those reported by the Department of Health and Human Services household survey shown in Figure 3.1 are probably due to differences in how the surveys were conducted. (Adapted from J.C. Anthony, L.A. Warner, R.C. Kessler. 1994. Comparative epidemiology of dependence on tobacco, alcohol, controlled substances, and inhalants: Basic findings from the National Comorbidity Survey. Experimental and Clinical Psychopharmacology 2:244-268.)