To the Editor From my perspective, the work by Johnson et al1 has 3 problems. Two are genuinely methodological, whereas the third is more related with the ethics of research. The 3 problems severely undermine the study’s scientific rigor.
First, the authors show that the use of complementary medicine (CM) is an independent variable associated with a greater risk of death. The problem arises when, after also adjusting for treatment refusal and delay from diagnosis to treatment, CM no longer has a statistically significant association with the risk of death. This means that the supposed association between CM use and survival is a spurious one, ie, a false correlation between 2 variables that is caused by a third variable.