Referred to by scientists as the “hormone of darkness,” melatonin is naturally produced by a gland in the brain at night, but it can also be purchased at any major drugstore, reports Mother Jones.

A sleep specialist recommended I try some six years ago, when I came to her office in desperation after months of tossing and turning. I was skeptical but figured I’d give it a shot; no prescription was needed, and Walgreens sold bottles for about $10. I swallowed a 3-milligram pill before bed and nodded off within minutes of lying down. Melatonin felt like a miracle—and I started taking it every night.

An estimated 50 to 70 million Americans have a sleep disorder. According to the National Center for Biotechnology Information, between 2002 and 2012 there was an 8 percent increase in adults and a 31 percent jump in young adults who experienced insomnia or trouble sleeping. Melatonin has gained a reputation as a safe, natural remedy, especially compared with drugs like Ambien that can be habit-forming and have more serious side effects. From 2007 to 2012, the number of adults using melatonin more than doubled to 3.1 million people, while the number of kids taking it increased by 482 percent. And sales of the hormone grew 20 percent annually for three years after that, according to the Nutrition Business Journal.