Clinical trials are not new. In fact, there are historical records that show that primitive clinical studies were already being conducted years B.C. The Old Testament describes how, under King Nebuchadnezzar II’s orders, the royal princes followed a specific diet; after some time, he noticed that these individuals were healthier than the ones who followed a different diet.
The first controlled clinical trial was carried out in 1747 by James Lind. Trying to combat scurvy, he included a supplement in the diet of several sailors who suffered from the disease while they were at sea. He divided the sailors into six groups, and he gave each group a different element: sulfuric acid, vinegar sea water, citrus fruits, and spice and barley water. After some weeks, only the group which received the citrus fruits was healthy and fit for duty; thus confirming the hypothesis that these fruits (due to their Vitamin C content, then unknown by Lind) could be used to treat scurvy.
After this, clinical trials grew more popular and began to evolve. Sir Ronald A. Fisher, for example, published articles on the importance of randomization, replication, blocking, and the use of factorial experiments. The first randomized, curative trial was carried out by Sir Geoffrey Marshall between 1946 and 1947 to test streptomycin and its efficacy in treating pulmonary tuberculosis.
Clinical research can be divided into two broad categories: clinical trials and observational studies.