Nightlight At The End Of The Tunnel

My boyfriend thinks there's something wrong with me because of how much I sleep. I've always needed to sleep a lot (like, nine hours). I've been tested for everything, and I'm fine. Do some people just need more sleep? How do I get him off my back?

--Duvet-Covered

Okay, so you're the love child of Rip Van Winkle and a log. Studies on identical twins suggest that our "sleep duration" (how long we tend to sleep) is between 31 and 55 percent "heritable" -- which is to say factory-installed, driven by our genes. Beyond your boyfriend not being tuned in to the genetics, there's a little-known feature of our immune system -- basically the psychological version of that plexiglass partition in liquor stores in bad neighborhoods -- that may be causing him to worry about your sleepathons. In addition to warrior cells being sent out by our immune system to attack bodily invaders, such as viruses, psychologist Mark Schaller's research suggests we have a psychological warning system -- the "behavioral immune system" -- to help us avoid being exposed to disease in the first place. This warning system gets triggered by, among other things, atypical behavior -- for example, sleeping far more than most people. To get your boyfriend off your case, you might tell him that being adequately rested is actually associated with lower risk of heart disease, obesity, and psychiatric problems. In fact, it's even associated with less risk of early mortality -- despite the things your boyfriend probably yells in bed: "Hey! Hey! You still alive? Should I call 911?"