A clinical trial gone awry: the Chocolate Happiness Undergoing More Pleasantness (CHUMP) study.

The randomized controlled trial is the "gold standard" for evaluating the benefits and harms of interventions. The Chocolate Happiness Undergoing More Pleasantness (CHUMP) study was designed to compare the effects of dark chocolate, milk chocolate and normal chocolate consumption on happiness. Although the intention-to-treat analysis showed that participants who received either dark or milk chocolate were happier than those who received no additional chocolate, the actual-consumption analysis showed that there were no differences between any of the groups. The reason for this result is that many participants switched groups mid-study because of their personal chocolate preferences. Although the CHUMP study was pleasurable, it demonstrated the difficulties associated with performing a truly blinded clinical trial.