observed in health status. The impact of an intervention may also be influenced by when it reaches an individual because there appear to be "critical periods" in human development. Certain interventions in childhood, for example, may have long-delayed yet long-lasting results. In addition, the population effects of interventions are important to consider. Small changes at the individual level may have important ramifications when applied to a whole community (Rose, 1992).

Community Interventions

The literature on community interventions is diffuse and difficult to summarize. A few observations based on that literature were shared with the committee. For example, the Healthy Cities/Healthy Communities activities demonstrate that a high level of interest in community interventions exists, but these activities have not yet generated a body of evidence that will allow them to be replicated in other settings. Study designs rarely meet high scientific standards. Although literature on advocacy and the process of community change abounds, validation through outcomes research is often lacking. Information linking process with outcome is inadequate, as are details describing implementation of interventions.

It was suggested that evidence that interventions have had a positive impact on the population is more likely to emerge in narrowly defined areas such as increasing immunization rates or decreasing workplace smoking. Similarly, one-time accomplishments are easier to document than what is needed to sustain activities. Literature examining the difference between attaining goals and maintaining them is lacking, and this issue requires more attention.

Targets for Intervention

The traditional targets for intervention have been specific diseases or behaviors. The field model of the determinants of health suggests consideration of a wider array of targets. For example, if adolescents' sense of well-being can be improved by reducing their feelings of alienation and hopelessness, can unintended pregnancies, alcohol and other drug use, crime, and the school dropout rate all be reduced? A multidimensional approach would be required, focusing on education, social and community involvement, family preservation, and improved social networks for teens and



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