03 26 19 — Science
Morning wood, pitching a tent, sunrise salute—there are a lot of names for it, but what exactly causes a morning erection?
For people with penises, nocturnal penile tumescence—as it’s officially called—is something that tends to, well, pop up regularly. And while it could be easy to dismiss it as the lingering response to a sexual dream, the fact is that such erections can occur as early as in the womb, so it’s not always related to arousal.
So why do they occur? Research shows that it usually happens during the REM stage of sleep, when sympathetic stimulation (better known as fight and flight) shifts to parasympathetic stimulation (aka rest and digest), creating a nerve response that causes an erection. So one reason why people wake up with an erection is likely because that’s when they are coming out of REM sleep. Interestingly, since we experience many sleep cycles in one night, some people will have up to five erections in the same stretch of slumber.
Additionally, testosterone levels are generally at the highest in the morning, which can stimulate an erection. But you also might find yourself involuntarily pitching a tent if you wake up with a full bladder, which can put pressure on the nerves in the spine that generate erections. In both cases, there’s a good chance that you may not actually feel any drive to have sex, even though your penis indicates otherwise …
Read more about what causes morning erections.