View Single Post
Old 08-22-2004, 02:37 PM
Colibri Colibri is online now
SD Curator of Critters
Join Date: Oct 2000
Location: Panama
Posts: 38,208
Originally Posted by E. Thorp
I don't have a good cite handy (a hint is found in this abstract), but I've read before that erections are a normal part of REM sleep, irrespective of the subject matter of dreams.
This is correct. Males normally have penile erections during REM (or dreaming) sleep. (And females have clitoral erections.) This reaction is so typical that it is used as a diagnosis of whether or not problems with erectile function are due to an organic cause or are psychological in nature. Men with an organic cause (nerve damage, poor circulation) will fail to have erections during sleep, while those with a pyschological cause will continue to have them.

From here:

From early childhood onwards, erections occur during sleep. This phenomenon, called nocturnal penile tumescence, occurs during REM sleep (Rapid Eye Movement) and usually occurs for about 100 minutes a night. Having an erection upon wakening in the morning is an example of this phenomenon.
An erection on waking up is not due to the need to urinate - this is merely coincidental. It just means you have been dreaming shortly before waking. Think about it - do you get an erection when you have to urinate when you're awake?

With regard to "restricted blood flow," these erections occur regardless of which position you sleep in.