Well, pillow-stackers, I’ve got news: You’re doing it wrong, and it all comes down to maintaining proper sleep hygiene. The most important thing, no matter your sleep style, is supporting your neck and helping to keep your body aligned so as not to cause spine problems; having your head crane too far forward or backward can cause pain and muscle strains. As the Cleveland Clinic puts it, “A pillow should keep your neck parallel to the mattress.” Three pillows = not parallel.
I personally rotate between sleeping on my back and sleeping on my sides. According to WebMD, thinner and firmer pillows are the right choice for me because they keep my head from being tilted too far forward when I’m on my back and help “fill in the distance between the ear and outside shoulder” when on my side, keeping proper spine alignment. That’s not to say that my “one pillow only” stance is the be-all and end-all. The University of Rochester Medical Center suggests adding extra pillows — but not under your head. For back sleepers, they note that a pillow under your knees can aid in supporting the spine, and for side sleepers, a pillow between the legs can “reduce stress on your hips and lower back.”
For those stomach sleepers out there, the pillow equation gets even more complex. Turns out, having a pillow for your head at all might not be the best move. Because of the importance of maintaining spinal alignment, the experts at Rochester note that you should add a pillow under your stomach and hips instead, and use a very flat pillow for your head if you insist on having one.