If you have sleep problems but can’t get relief from nondrug approaches (such as sticking to a regular bedtime/wake-up schedule—regardless of how you sleep—and by keeping your bedroom cool, dark and quiet), then you may decide to try a sleeping pill. Roughly nine million Americans rely on drugs such as zolpidem (Ambien) for chronic insomnia.

A surprising quirk to sleep medication: It may be possible to cut your dose in half and still get good sleep while also reducing risk for side effects (and costs).

In a recent study of 74 adults, those who used half as much of the drug (alternating a 10-mg dose of zolpidem with a placebo each night) slept just as well as those who took the full dose every night. How could this be? People expect to sleep better when they take a pill that has worked before—even when some of the pills happen to be placebos, explains Michael Perlis, PhD, a sleep specialist and the study’s lead author.

The study looked only at zolpidem, but it’s likely that the same approach will work with other medications, including over-the-counter sleep aids such as Benadryl, he says.

What the study researchers suggest: If you require medication to sleep, start with a standard dose. After about a month—assuming that your sleep is reliably improved and your doctor agrees—cut the dose by 50%. You can ask your doctor to change, say, a 10-mg dose to 5 mg…or better yet, ask your pharmacist to create a foil pack—half of which is your original dose and half of which is placebos (in matching capsules). You are likely to find that you’re sleeping just as well!