Naps don’t work for everyone. Genetic differences are why.

Allison Hirschlag:

Everyone likes a good nap now and then, right? Whether you nod off during a boring movie, or rest your head on your desk at work for 20 minutes or so to fight the afternoon slump, naps can revitalize you in a major way.

One study even showed they can boost performance and memory regulation better than caffeine. This all sounds great in theory, but many people — myself included — find naps do the opposite.

I wake up from naps feeling like I’m in the throes of a New Year’s Day-strength hangover. It takes me at least 20 minutes to recover from them, and I never end up seeing any of the benefits. Even when I timed my nap to be no more than 30 minutes — the nap length sleep experts claim is the most beneficial — I came out of it certain I was experiencing the early stages of the flu (I wasn’t).