During the drug approval process, pharmaceutical drugs undergo numerous clinical and epidemiological trials. While most consumers understand that these studies are conducted to confirm the safety of a drug, the differences between the two are not always as clear.

Clinical Trials

Clinical trials are health-related research studies which confirm or discredit the safety of a drug by following pre-defined protocols. These trials are a way for pharmaceutical companies and governmental agencies to collect safety and efficacy data. According to the National Institutes of Health, there are five different types of clinical trials; treatment trials, prevention trials, diagnostic trials, screening trials, and quality of life trials. Treatment trials are utilized by pharmaceutical companies to test new drugs or experimental treatments. Prevention trials aim to improve the longevity of a healthy individual's life, and may involve the testing of medications and vaccines. Diagnostic, Screening, and Quality of Life trials are conducted to find better tests or procedures for diagnosing a particular disease or condition, test the best way to detect certain diseases or health conditions, and to explore ways to improve comfort and the quality of life for individuals with a chronic illness

The protocol for clinical trial testing occurs in three phases:

• Phase 1 uses 20-80 healthy volunteers to establish a drug's safety and profile. (about 1 year)
• Phase 2 employs 100-300 patient volunteers to assess the drug's effectiveness. (about 2 years)
• Phase 3 involves 1000-3000 patients in clinics and hospitals who are monitored carefully to determine effectiveness and identify adverse reactions. (about 3 years)

Epidemiological Studies

The first step in an epidemiological study is to strictly define exactly what requirements must be met in order to classify someone as a case. According to the Reference Guide on Epidemiology, "epidemiology is concerned with the incidence of disease in populations and does not address the question of the cause of an individual's disease. This question, sometimes referred to as specific causation, is beyond the domain of the science of epidemiology. Epidemiology has its limits at the point where an inference is made that the relationship between an agent and a disease is causal (general causation) and where the magnitude of excess risk attributed to the agent has been determined; that is, epidemiology addresses whether an agent can cause a disease, not whether an agent did cause a specific patient's disease." The strength of an epidemiological study depends on the number of cases and controls included in the study. The more individual cases that are included in the study, the more likely it is that a significant association will be found between the disease and a particular risk factor.

There are four main types of epidemiological studies:

• Cohort Study: a study in which subjects who have a certain condition and receive a particular treatment are followed over time and compared with another group who are not affected by the condition under investigation.
• Case Control Study: investigates the prior exposure of individuals with a particular health condition and those without it to infer why certain subjects, the "cases," become ill and others, the "controls," do not.
• Occupational Epidemiological Study: designed using any standard epidemiological study and incorporating working individuals with particular jobs or exposures as subjects.
• Cross-Sectional Study: compares groups in terms of their current health and exposure status and assesses their similarities.

While both types of studies have advantages and disadvantages, it is advantageous for pharmaceutical companies to conduct both, in an attempt to safeguard consumers. Generally, the results of clinical trials are manipulated more often than epidemiological studies, as the Food and Drug Administration (FDA) relies more heavily on clinical trials for drug approval.