The idea of “getting your beauty sleep” may sound old fashioned—something your grandma might have said to your mom, an old wives’ tale to get little girls to go to bed. But modern science is 100% on Grandma’s side. Beauty sleep is as real as it gets.

The Truth About Beauty Sleep – How It Works:

It all has to do with the hormones the brain excretes—and those it suppresses—during sleep. Though REM sleep is widely known as the brain’s magic elixir, Stages 3 and 4, known as deep non-REM sleep, are when the human growth hormone is produced, which is a major agent for keeping skin healthy. Growth hormone is so good at repairing and restoring skin that getting injections of it has become a Hollywood fad. But what celebrities spend thousands of dollars at their local plastic surgeon, you can get for free with an excellent night of sleep.

The flipside, of course, is that missing out on your beauty sleep can have extremely detrimental effects on your appearance. While the brain in deep sleep is pumping out growth hormone, it’s also suppressing cortisol, a stress hormone. While cortisol is necessary for a few important functions, in excess it wreaks havoc on the skin and body, leading to weight gain, acne, eczema, and even hair loss. A 4-hour night of sleep increases cortisol production by a whopping 37%—as if you weren’t already stressed out enough.

Get Some Sleep to Look Your Best

The effects of sleep deprivation on your looks aren’t just theoretical. A few major studies have shown that we can perceive the effects of sleep deprivation in others; one such study found that we view people who are sleep deprived as 6% less healthy, 4% less attractive, and 19% more tired. Even if an energy-drink-and-coffee cocktail in the morning perks you up enough to get through the day, your face can’t be fooled. Sleep is the only remedy.

Best Mattress Reviews has produced a brand-new infographic on the benefits of beauty sleep—and the harmful effects of missing out on it. Check it out for the full scoop on the most up-to-date science, as well as practical tips for sleeping and looking your best