Chronic pain treatment preferences change following participation in N-of-1 trials, but not always in the expected direction.

Objective: To examine pain treatment preferences before and after participation in an N-of-1 trial.

Study Design And Setting: In this observational study nested within a randomized trial, we examined chronic pain patients' preferences before and after treatment in relation to N-of-1 trial results; assessed the influence of different schemes for defining comparative "superiority" on potential conclusions; and generated classification trees illustrating the relationship between pre-treatment preferences, N-of-1 trial results, and post-treatment preferences.

Results: Treatment preferences differed pre- and post-trial for 40% of participants.