The strong belief that chocolate consumption leads to more happiness was not observed in the CHUMP study. A far more important indicator of happiness appears to be “getting what you want, when you want it.” As shown by the intention-to-treat analysis in , participants in the dark chocolate or milk chocolate intervention groups were far more likely to be happy. However, once the participants who had changed groups during the course of the study were accounted for, there was no significant difference in happiness among the 3 groups. This suggests that people who were most unhappy with the “no chocolate” intervention were more likely to switch to the dark or milk chocolate groups.
There are several limitations of the CHUMP study. One participant noted in the post-study interview: “My selection into the ‚no chocolate' group led to utter disappointment, and I made an all-out attempt to get at least a few chocolate bars for free.” Thus, participant randomization and subsequent recognition of being in the “no chocolate” group may have adversely affected the happiness measures.
Second, the fact that the study period overlapped with Halloween may have adversely affected the overall consumption of chocolate during the study, and this may have led to crossover contamination.
Third, I made no attempt to control for other possible sources of happiness, such as the other basic “Cs” of happiness: candy, chips, cookies, caffeine and cola. Although consumption of any of these Cs would have led to happier participants, it may have had additive or multiplicitative effects with chocolate consumption leading to biased results.
In conclusion, the CHUMP study shows the pitfalls of running a clinical trial in 1 locale. Crossover and contamination of the study groups are easily achieved when taste buds are involved. However, despite the problems of running a clinical trial, there is one advantage: the author has a year's supply of chocolate left in his basement. Ah, happiness!
Kevin Chan MD MPH Pediatric emergency physician Toronto, Ont.