(AP) — A quirky new study suggests patients’ expectations can make a big difference in how they feel after treatment for a migraine.

Boston researchers recruited 66 patients, and gave them either a real medication to use when migraines struck or a dummy pill. Sometimes they knew what they were taking; sometimes researchers secretly switched the pills.

The study found that it’s important for doctors to give a positive message along with a medication: Patients reported more pain relief when they accurately believed they were taking the real drug than when they were told, falsely, that it was a fake. But even the placebo offered some pain relief, more when patients thought it was the real thing.

The study was published Wednesday in the journal Science Translational Medicine.