Estimating the Prevalence of Substance Abuse with Social Indicators

Article excerpt

Governments are increasingly interested in estimating the prevalence of substance abuse with social indicators, largely because of the high cost of estimating prevalence with surveys of random samples of the population. With both the individual and county as the unit, we regress measures of the use of alcohol, marijuana, and other drugs on social indicators that fall into three categories: demographics, measures of social disorganization, and measures more directly related to the use of substances. The measures of explained variance are fairly low, but even more troubling is that the effects of several social indicators are in the "Wrong" direction. Reliance on social indicator data to supplant survey estimates of the prevalence of substance abuse requires further validation, attention to sources of bias in the indicator data, and replication of the models over time.

Collection of information on substance use is vitally important for planning prevention and treatment, allocation of resources, and evaluation of programs. Surveys of random samples of the population provide excellent means of estimating the prevalence of use of substances except for those which tend to be very rare, negatively sanctioned, or used by those who are difficult to sample. Estimating the prevalence of alcohol use with sample surveys is quite successful; estimating the prevalence of heroin use with sample surveys is less successful (Simeone, Frank, & Aryan, 1993). But even for alcohol, sample surveys have the disadvantage of being fairly expensive, especially if the sample must be large enough to allow estimates for small areas such as counties. Concern over costs has led policy makers to emphasize the development of methods of estimating the prevalence of substance abuse which would be substantially cheaper than surveys (Substance Abuse and Mental Health Services Administration, 1995, 1996).

One such effort, the social indicators approach, involves using data collected by various governmental agencies for diverse purposes to estimate indirectly the prevalence of substance abuse. The variables employed might be demographic factors (e.g., sex and age distributions), indicators of social disorganization (e.g., poverty and school dropout rates), or more direct indicators of substance use (e.g., drug and DWI arrest rates). These data are inexpensive to compile since they are routinely collected. The use of social indicators avoids the problem of basing rates of prevalence on small survey samples, since the indicators are based on the population within a specific geographic area; the denominator for each rate is the number of people at risk of experiencing the event, so the problem of inferring from small samples to the entire population is moot.

While there are several salutary aspects of the social indicator approach, it does have its potential limitations. In comparing social indicators across specific geographic areas, comparability of measures and procedures is crucial in order to ensure that differences reflect actual variation rather than methodological artifacts. Because the measures comprising social indicators are typically collected for purposes other than estimating levels of substance abuse, the comparability of measures in different geographic areas is unknown. In addition, local conditions such as population shifts, natural disasters, tourism patterns, and law enforcement resources and priorities can significantly affect the indicators within a given geographic area. Because there may be numerous and competing explanations for differences between geographic areas and even within a geographic area over time, more direct and systematic methods, such as surveys, may be needed. Joseph and Hollett (1993, p. 813) note that without "knowledge of local social geography, applications of indicators methodologies run the risk of being `black boxes."'

Systematic investigations assessing the concordance of survey and social indicator data in estimating the prevalence of substance abuse are warranted. …