I frequently see the claim that humans respond differently to the same medication, and I believe this is true.
Can we discuss how one would prove this & quantify it?
You enroll 500 participants with BP > 150/90 mm Hg, randomize them to active drug or placebo, and measure BP later.
I believe some attribute inter-individual differences in change from baseline in the treatment arm to differences in drug effect. This seems completely silly, as highlighted by the fact(?) that you’d find inter-individual differences in change from baseline in the placebo arm. You would also find inter-individual differences in change from baseline if you enrolled, gave no treatment, and simply re-measured BP later, so say I anyway. Life is noisy, measurements are imperfect, and regression toward the mean has a relationship with the initial value.
First, are my intuitions above correct? Second, in your field of interest, has actual treatment effect heterogeneity been measured in a meaningful way? Can you share a reference? It seems a cross-over study of different drugs administered in random order to a group of people would be needed to comment on whether there are actual interindividual differences in drug response? Is that so?