What's up with morning erections?

Hi Alice,

Why is it when guys wake up they have an erection in the morning? Does this happen to ALL guys? Thanks.

Dear Reader,

Contrary to what many believe, waking up with a flag at full mast isn’t the first time it’s at attention during the day. Morning erections are technically referred to as interrupted nighttime erections (or nocturnal penile tumescence), which can happen three to five times per night. They usually pop up (pun intended) during periods of rapid eye movement (REM) sleep and last around 30 minutes each. Those with penises who are older than 60 years may even have them during non-REM sleep. Unlikely due to urine buildup in the bladder or dream content, they’re both common and completely normal.  

These spontaneous woodies in the wee hours are thought to be caused by a combination of factors, including a shift from the sympathetic (fight or flight) nervous system to the parasympathetic (rest and digest) system. The parasympathetic nervous system is responsible for the body’s resting state. In fact, the parasympathetic nervous system is most active when you’re asleep. A common theory for nocturnal erections is that a full bladder can stimulate the sacral nerve (which runs from the brain to the pelvic area), a part of the nervous system, which then leads to an erection. Furthermore, the REM phase of sleep is when folks are most likely to dream, erotically or otherwise, potentially causing a full mast. Another factor that may contribute to pitching a mini tent is testosterone; it’s been correlated with a greater frequency of nighttime erections, and it’s at its highest levels in the morning — go figure. Similarly, yet less visually noticeably, those with vaginas experience REM-related engorgement of the clitoris and vagina as well. So despite the name, the common experience of "morning wood" has nothing to do with time of day, but rather the individual’s stage of sleep upon waking. 

All that being said, nighttime stiff ones are common, typical experiences and generally aren't causes for worry. In fact, they’re a sign that the penis is in good working order. For those finding that they're not having any, it could be a sign of an underlying condition, such as diabetes, or a psychological ailment, such as depression. However, since erections are linked to sleep quality, they might not occur every night, even in healthy individuals. If morning wood, or any erection for that matter, lasts longer than four hours, it’s recommended to speak with a health care provider.  

Last updated Jan 24, 2020
Originally published Jun 11, 1999

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