# Morning erections and full bladders -- Correlation? Causation? **URL:** \ **Category:** Factual Questions\ **Created:** [September 12, 2006, 4:16pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429 "2006-09-12T16:16:24Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 12, 2006, 4:16pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/1 "2006-09-12T16:16:24Z")
Inspired by [this](http://boards.straightdope.com/sdmb/showthread.php?t=387863) thread. That’s all IMHO, but I’m looking for medical facts, not amusing anecdotes. Is there any sound **medical** evidence that morning erections are Mother Nature’s way of waking you up to pee? ---
**Author:** ![Bongmaster](https://avatars.discourse-cdn.com/v4/letter/b/6a8cbe/32.png) [@Bongmaster](https://boards.straightdope.com/u/Bongmaster)\ **Post date:** [September 12, 2006, 4:56pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/2 "2006-09-12T16:56:47Z")
Not at all. From what I have read the morning erection is a natural function of the penis which facilitates the distribution of oxygen. Basically if you don’t get hard on a regular basis you won’t get enough oxygen down there so the body automates it to some degree. No cite for you but if you look around on google I’m sure you’ll find more info. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [September 12, 2006, 5:19pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/3 "2006-09-12T17:19:25Z")
It might have something to do with the contents of your bladder, but it’s definitely related to REM sleep. See [this old thread](http://boards.straightdope.com/sdmb/showthread.php?t=354820) for more discussion. ---
**Author:** ![chappachula](https://avatars.discourse-cdn.com/v4/letter/c/d2c977/32.png) [@chappachula](https://boards.straightdope.com/u/chappachula)\ **Post date:** [September 12, 2006, 5:52pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/4 "2006-09-12T17:52:46Z")
> [@](#): > > Morning erections and full bladder **s** umm…I just had this weird thought… how many bladders do you have? ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 12, 2006, 5:59pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/5 "2006-09-12T17:59:16Z")
> [@chappachula](#): > > umm…I just had this weird thought… > how many bladders do you have? I’m more interested in talking about how many (simultaneous) erections I have. ---
**Author:** ![RealityChuck](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/realitychuck/32/195_2.png) [@RealityChuck](https://boards.straightdope.com/u/RealityChuck)\ **Post date:** [September 12, 2006, 6:04pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/6 "2006-09-12T18:04:43Z")
Yes. The connection is due to \*post hoc ergo propter hoc. \*:rolleyes: ---
**Author:** ![panache45](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/panache45/32/64_2.png) [@panache45](https://boards.straightdope.com/u/panache45)\ **Post date:** [September 12, 2006, 8:14pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/7 "2006-09-12T20:14:15Z")
What would you accept as “\*\*medical \*\*evidence”? If I tell you that I have an erection even after a short nap, and even when I don’t need to urinate, would that fact qualify as “\*\*medical \*\*evidence,” or do a need a note from my doctor? ---
**Author:** ![Cheesesteak](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/cheesesteak/32/3694_2.png) [@Cheesesteak](https://boards.straightdope.com/u/Cheesesteak)\ **Post date:** [September 12, 2006, 8:27pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/8 "2006-09-12T20:27:58Z")
> [@panache45](#): > > What would you accept as “\*\*medical \*\*evidence”? If I tell you that I have an erection even after a short nap, and even when I don’t need to urinate, would that fact qualify as “\*\*medical \*\*evidence,” or do a need a note from my doctor? I sometimes get erections without being asleep, therefore sleeping and erections are unrelated? The fact that men regularly get erections while sleeping does not say a thing about whether or not a full bladder can be a cause of morning wood. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 12, 2006, 8:52pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/9 "2006-09-12T20:52:14Z")
> [@panache45](#): > > What would you accept as “\*\*medical \*\*evidence”? If I tell you that I have an erection even after a short nap, and even when I don’t need to urinate, would that fact qualify as “\*\*medical \*\*evidence,” or do a need a note from my doctor? Something from a medical white paper, or the NEJM, or something by an actual MD, would be more acceptable than anecdotal “data.” The fact that a nap can give you a bone on an empty bladder, yeah, that’s a good anecdote. I would also look at some sound logic. For instance, women, who get no erections at all, are still able to tell, even when fully awake, when they need to tinkle. To me that’s a good bit of logic that says, at least, a hot throbbing member is not Mother Nature’s _only_ way of telling us to get the key from the receptionist. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 12, 2006, 8:53pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/10 "2006-09-12T20:53:15Z")
> [@Cheesesteak](#): > > The fact that men regularly get erections while sleeping does not say a thing about whether or not a full bladder can be a cause of morning wood. Right. Correlation is not causation. Necessarily. ---
**Author:** ![ultrafilter](https://avatars.discourse-cdn.com/v4/letter/u/3d9bf3/32.png) [@ultrafilter](https://boards.straightdope.com/u/ultrafilter)\ **Post date:** [September 12, 2006, 8:55pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/11 "2006-09-12T20:55:19Z")
> [@tdn](#): > > women, who get no erections at all When you’re at home, google on the phrase “clitoral erection”. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 12, 2006, 9:08pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/12 "2006-09-12T21:08:14Z")
> [@ultrafilter](#): > > When you’re at home, google on the phrase “clitoral erection”. Why, are there good pictures? I’m aware of that, actually, but I’ve just never heard of a woman talking about having a piss-hard of her own. ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [September 12, 2006, 9:31pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/13 "2006-09-12T21:31:04Z")
I don’t think I am the only one that has this experience but I think there is some misunderstanding of the term. The key factor isn’t whether one happens without the other or vice-versa. The key trait is that the bone is locked in place at a time when it is needed to switch duty. The need to pee seems to sustain it and make other business more difficult. ---
**Author:** ![daffyduck](https://avatars.discourse-cdn.com/v4/letter/d/ec9cab/32.png) [@daffyduck](https://boards.straightdope.com/u/daffyduck)\ **Post date:** [September 12, 2006, 9:51pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/14 "2006-09-12T21:51:01Z")
Testoserone levels are also highest in the early morning. It seems likely that could be a contributing factor. From [here](http://www.fortysixty.org/12.html): Testosterone levels rise and then fall over a 24-hour period. Levels are highest first thing in the morning (usually around 5 am) and are lowest late in the afternoon. ---
**Author:** ![feppytweed](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/feppytweed/32/4280_2.png) [@feppytweed](https://boards.straightdope.com/u/feppytweed)\ **Post date:** [September 12, 2006, 9:54pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/15 "2006-09-12T21:54:22Z")
> [@chappachula](#): > > how many bladders do you have? Well, I have a urinary bladder and a gallbladder… just sayin’. ---
**Author:** ![Marley23](https://avatars.discourse-cdn.com/v4/letter/m/45deac/32.png) [@Marley23](https://boards.straightdope.com/u/Marley23)\ **Post date:** [September 13, 2006, 1:23am UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/16 "2006-09-13T01:23:10Z")
I doubt there’s a connection: it’s difficult (if not impossible) to pee when you’ve got an erection, so it’d be a lousy ‘warning system.’ ---
**Author:** ![Shagnasty](https://avatars.discourse-cdn.com/v4/letter/s/9dc877/32.png) [@Shagnasty](https://boards.straightdope.com/u/Shagnasty)\ **Post date:** [September 13, 2006, 1:49am UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/17 "2006-09-13T01:49:14Z")
> [@Marley23](#): > > I doubt there’s a connection: it’s difficult (if not impossible) to pee when you’ve got an erection, so it’d be a lousy ‘warning system.’ That was my whole point and my interpretation of the pee hard-on phenomenon. You have to pee badly but you have a hard-on which greatly decreases flexibility and points the thing in an altogether inappropriate direction. Furthermore, the hardone won’t go away because it is locked in place by the strong need to pee. It is a chicken and egg, Catch-22 problem all stuffed into one. ---
**Author:** ![danceswithcats](https://avatars.discourse-cdn.com/v4/letter/d/9e8a1a/32.png) [@danceswithcats](https://boards.straightdope.com/u/danceswithcats)\ **Post date:** [September 13, 2006, 2:12am UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/18 "2006-09-13T02:12:21Z")
> [@ultrafilter](#): > > It might have something to do with the contents of your bladder, but it’s definitely related to REM sleep. See [this old thread](http://boards.straightdope.com/sdmb/showthread.php?t=354820) for more discussion. What if I have Nine Inch Nails or Stone Temple Pilots sleep? ---
**Author:** ![Dr\_Paprika](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dr_paprika/32/3042_2.png) [@Dr\_Paprika](https://boards.straightdope.com/u/Dr_Paprika)\ **Post date:** [September 13, 2006, 5:08am UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/19 "2006-09-13T05:08:55Z")
I think the connection is tenuous. A full bladder might wake you up regardless of whether the erection is there or not. Erections are usually do to the action of the parasympathetic nervous system, which performs “housekeeping” functions like cleaning out the bowel and emptying the bladder. The “fight or flight” sympathetic nervous system tends to cause urinary retention, etc. I suppose you could argue that your bladder fills while you sleep, the parasympathetic system acts to encourage you to empty it, and an erection might also result just before waking up. But you hardly get an erection every time the bladder’s full. ---
**Author:** ![tdn](https://avatars.discourse-cdn.com/v4/letter/t/94ad74/32.png) [@tdn](https://boards.straightdope.com/u/tdn)\ **Post date:** [September 13, 2006, 1:06pm UTC](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429/20 "2006-09-13T13:06:56Z")
> [@Shagnasty](#): > > Furthermore, the hardone won’t go away because it is locked in place by the strong need to pee. I agree with your post completely except for this bit. Does the need to pee actually lock the hardon in place, or does it just seem that way? [Next page](https://boards.straightdope.com/t/morning-erections-and-full-bladders-correlation-causation/372429.md?page=2)