Home Section D - Opinion Ask Dr. P

Ask Dr. P


Dear Dr. P: Some of my male friends and I were discussing the phenomenon that is referred to as “morning wood.”  I had some questions about it that they couldn’t answer, even though it happens to their own bodies.  What is the actual scientific explanation for morning wood?

Dear Woody,

I could say that “morning wood” consists of twigs, broken dry branches, sticks and small split logs gathered to make the fire in an old kitchen stove to cook breakfast for farm hands—but it’s really knot.

What you and your male buddies are questioning are morning erections noticed upon awakening.  An old and erroneous belief was that these erections were due to stimulation from the pressure of a full bladder, but this is not at all the case.  A similar phenomenon of sexual arousal and vaginal lubrication occurs among females also in the mornings, but this often goes without notice—for obvious reasons.

Both phenomena occur because of involuntary physiological vasocongestion and tumescence from an increase blood flow in the penis-scrotum or vulva-vagina that occurs periodically through the night. This happens in all normal and healthy male and female human beings from before birth to our death.  Every 90 minutes while we sleep we enter a stage called Stage-1 REM sleep.  REM sleep can last from 5 to 30 minutes, with the longer of our 3 or 4 nightly periods of REM sleep occurring toward morning when we might awaken.  REM sleep shows several correlated distinctive physiological and cognitive events.

The following occurs in Stage-1 REM sleep: 1) an 80 percent reliability of a report of dreaming if awakened during REMs; 2) rapid eye movements (REMs) which are visible through the closed eye-lids as scans and jumps of the eyes as if looking at a scene (you were looking at the content of your dream); 3) a fast low-voltage brain wave or rhythm that indicates alertness and attentiveness; 4) physiological arousal as in fast heart rate, warm skin temperature, quicker breathing and sometimes twitches and mumblings; 5) an overall total muscular paralysis that prevents the dreamer from acting out the dream—with the exception of the small twitches; and of course 6) sexual arousal with vaginal lubrication in females and the erection or “morning wood” you mentioned in males.

The dreams do not have to have a sexual content for the lubrication or erections to occur.  If the dream content was sexual, they sometimes, but do not necessarily result in an orgasm in both males and female.  At that time a nocturnal emission of semen can occur in males.  It is only because morning awakenings have occurred during or shortly after the end of a REM period dream that the morning (“Woody”) erections are noticed.  If the REM period ends some time prior to awakening, the dream is not recalled and the erection has subsided.

Morning erections tend to be more complete and longer-lasting than at any other time of day, as is male libido at its peak in the mornings, due to a daily testosterone surge that occurs in the early morning hours.

These phenomena are nature’s way of exercising a physiological system, even if a person does not do so otherwise.

Not pileatedly yours,

Dr. P


Previous articleDear Sue
Next articleGun Rights