Sweden found a similar elevated risk of poor health for residents of lower socioeconomic status communities, controlling for age, sex, education, body mass index, smoking, and physical activity (Malmstrom et al., 1999).

Correlational and observational studies suffer well-known weaknesses with respect to making causal inferences. It may be, for example, that individuals with poor health selectively migrate to or are left behind in poor neighborhoods. In the case of individual selection, the correlation of health with community characteristics may be spurious. Experimental and quasi-experimental studies have thus begun to explore community-level effects on health outcomes. One such example is found in the Moving to Opportunity (MTO) program, a series of housing experiments in five cities that randomly assigned housing project residents to one of three groups: an experimental group receiving housing subsidies to move into low-poverty neighborhoods, a group receiving conventional (Section 8) housing assistance, and a control group receiving no special assistance. A study from the Boston MTO site showed that children of mothers in the experimental group had significantly lower prevalence of injuries, asthma attacks, and personal victimization during follow-up. The move to low-poverty neighborhoods also resulted in significant improvements in the general health status and mental health of household heads (Katz et al., 1999). Because the experimental design was used to control individual-level risk factors, a reasonable inference from these studies is that an improvement in community socioeconomic environment leads to better health and behavioral outcomes.

In short, research in social and behavioral science has established a reasonably consistent set of findings relevant to the community context of health:

• There is considerable inequality between neighborhoods and local communities along multiple dimensions of socioeconomic status.

• A number of health problems tend to cluster together at the neighborhood and larger community levels, including but not limited to violence, low birth weight, infant mortality, child maltreatment, and the risk of premature adult death.

• These two phenomena are themselves related; community-level predictors common to many health-related outcomes include concentrated poverty and/or affluence, racial segregation, family disruption, residential instability, and poor-quality housing.

• The ecological differentiation of U.S. society by factors such as social class, cultural background, race, and health (see also Chapter 7) is a