I recently blogged about a surprising association between ALS and loss of a child: Losing a child reduces your chance of getting ALS. I wrote to the lead author of the study, Dr. Fang Fang, to ask how this study come to be. Here is his reply:
Severe emotional stress, as in the case of loss of a child, has previously been associated with health consequences such as psychiatric hospitalizations, cardiovascular morbidity, etc. Our initial hypothesis was that severe emotional stress might also contribute to the development of ALS. We thus used the unique settings in Sweden including the population based registration of in-patient hospitalizations and familial link registration to explore the relationship between loss of a child and the risk of developing ALS. It was surprising for us to see an inverse association between loss of a child and the risk of ALS. After a series of careful checks on data quality, we came to believe this association was not due to systemic errors.
In other words, they did the study because they expected the opposite result.