If you happen to’ve ever had bother falling asleep, odds are you’ve heard about (or tried) melatonin as a way to solve your insomnia. There are a multitude of ways to devour the sleep aid — from pills, to gummies. But melatonin diffusers, also known as vape pens, are the latest additions to the arsenal of products promising higher shut-eye. The first melatonin vape was introduced only 5 years ago. Because they’re so new, there aren’t many studies on the…