Morning wood, or, as your doctor would prefer you call it, nocturnal penile tumescence (NPT), is typical in every young guy. But you've probably woken up plenty of mornings with a somehow rock-hard penis and wondered why. Apparently, it's got nothing to do with having to pee.
"A guy in his 60s or 70s and wakes up and has to pee, and that doesn't happen anymore," says Joseph Alukal, MD, assistant professor of Urology and Obstetrics and Gynecology at NYU Langone Medical Center. "It's not directly related to that." But, weirdly enough, although researchers can tell us what doesn't cause morning wood, what does cause it is still kind of a mystery. "The penis is a very strange organ in terms of its job and the way it traps blood inside it," says Dr. Alukal. While the search for answers continues, here are some hypotheses.
1 | Your penis is going rogue because your brain isn't paying attention. According to a study by the Society for Endocrinology, it could actually be that as certain parts of the brain shut down during REM sleep, your brain is no longer keeping your penis in check. Whereas normally the brain is regulating the penis and making sure erections only occur when needed, during REM the penis is free to do whatever it wants. And what it wants to do is get hard.
2 | It's your hormones fluctuating. "In the morning, it's going to be the highest testosterone level he'll have all day," according to Dr. Alukal, noting that morning boners tend to stop when men reach their 40s and 50s and their testosterone levels dip. So it could just be that you're at your manliest (and hardest) in the morning.
3 | It's how your penis "exercises." NPT can actually be a way the body conditions the penis to keep blood in it for long periods of time. "There's no other place in your body that has to trap blood for an extended period of time," says Dr. Alukal. "For example, if we took a tourniquet and tied it around your foot for a half hour, we might have some problems afterwards. But your penis is expected to trap blood for a half hour or an hour and be fine afterwards. This could be part of the programming that reminds the penis, 'This is how you do your job.'" Think of it like weight training. If it weren't for nighttime boners, it's entirely possible you wouldn't be able to keep your boners for more than a few minutes at a time without it becoming incredibly painful. However, Dr. Alukal is quick to point out that this is just a theory, and there's no data to back it up.
4 | You rubbed up against something in your sleep and subconsciously got turned on. Just because you're waking up with a boner, it doesn't necessarily mean you've been dreaming about Jennifer Lawrence. The brain is still receptive to physical stimulation when its asleep, so sleeping close to a partner can absolutely set it off. "Your brain can still feel the stimulation and say, 'Hey wait a second, this guy needs an erection,'" says Dr. Alukal. So before you get out your dream analysis journal, consider that you might just be turned on by the hot bod next to you.