3. Studies in Pharmacoepidemiology and their classification

Epidemiologic studies often are divided into two types, descriptive and analytic, and each of these uses specific kinds of studies.

Descriptive studies examine patterns of disease occurrence, with a focus on person, place, and time. These studies use relatively accessible data to estimate caseloads, to determine the amount of public health resources needed, or to identify high risk groups. Descriptive studies are useful if very little is known about a new disease or condition. They can be used to generate hypotheses on risk factors and causes of disease that need to be confirmed or ruled out by analytic studies. For example, early descriptive studies found that the majority of newly diagnosed AIDS cases in the USA were among young men having sex with men, which led to the hypothesis that certain types of sexual behaviour might cause AIDS. The most basic types are: a case report, a case series, and an incidence study. These types of study involve no comparison group. They are merely descriptive.

Analytic studies aim to identify and evaluate determinants, causes or risk factors of diseases or health-related events. In contrast to descriptive studies, which generate hypotheses, analytic studies are used to test hypotheses. They are often employed to analyse the distribution of exposures and diseases and to look for and measure associations. These types of studies typically require more resources and expertise and can be rather complex. A key feature of analytic studies is that they involve comparison groups.