Example 1

A cinnamon-based herbal oil reduced breast pain in women compared to evening primrose oil. Commercial oils were used for the study. The new cinnamon oil was provided free to all participants, while the primrose oil needed a prescription to be filled by the patient.

In this example, there are several sources of potential bias, including:

  • Trial not blinded;
  • New medications are appealing;
  • False safety impression;
  • Impressions based on age;
  • Patient drop out; and
  • Self-fulfilling prophecy.