Review Question - QID 216654

This study that compares the rates of schizophrenia in different countries with different policies is most consistent with an ecological study.

An ecological study assesses the association between an exposure and an outcome at the population level. This population can be defined either geographically (state/country) or temporally (year). Exposure can either be assessed directly if reliable data are available or indirectly through examining legal or health structures if data are not available. Disease outcomes can be assessed using either incidence or prevalence. The major downside of ecological studies is known as the "ecological fallacy" where spurious associations between populations do not reflect the true risk profile at the individual level. For example, there is a strong negative association between the number of computers and the rate of malnutrition in countries; however, this does not imply that using a computer will prevent malnutrition.

Incorrect Answers:
Answer 1: Case-control studies are also observational studies that assess the association between a risk factor and a disease. These studies are performed by comparing patients with a disease and patients without that disease in terms of past exposures.

Answer 2: Cohort studies are also observational studies that assess the association between a risk factor and a disease. They both measure prevalence in the presence and absence of the risk factor; however, they are performed at the individual patient level rather than at the population level.

Answer 3: Cross-sectional studies are also population-level studies that capture a snapshot of the incidence of a risk factor and a disease; however, they attempt to stratify a single population by the risk factor rather than studying distinct populations across a geographic or temporal distance.

Answer 5: A factorial design study is an interventional study that attempts to assess the effect of multiple treatments at once. For example, a study in the treatment of cancer may test different combinations of 3 chemotherapeutic drugs in terms of rates of remission.

Bullet Summary:
Ecological studies test the relationship between an exposure and an outcome by measuring rates in geographically or temporally separated populations.