What's the Deal With 'Morning Wood'?

Editor's note: Some of the sources for this article requested their full names and locations not be used.

Chris, a 37-year-old living in New York, remembers the first time he woke up one morning with an erect penis. At age 11 or 12, he was a little freaked out.

"I woke up and kind of rolled onto it and that was not a great feeling," Chris remembered.

He didn't know the name of his spontaneous sleep erection at the time, but now he—like most Americans—refers to that daily experience as "morning wood."

The somewhat less catchy formal name for erections that occur during sleep is "nocturnal penile tumescence." Also, the slang term is slightly misleading as nocturnal penile tumescence typically occurs during nighttime REM sleep. It's just that people are more likely to become aware of these erections when they're awake.

Now, Chris experiences nocturnal penile tumescence regularly.

"It seems to have something to do with how restful my sleep was and what I have going on the following day," he mused. "In other words, a restful night with nothing pressing in the morning usually equals massive morning wood."

This sentiment was echoed by other men we spoke to about morning erections. But not all the comments were positive.

"Usually it only happens when I wake up with a full bladder," said Daniel, 37. "You would think I could take advantage of it to get some sexy time in with the missus in the morning, but as soon as I pee, it goes away and that's that."

"It's not pleasurable at all," Saurabh, 30, from Houston, clarified. "Like, I don't wake up and think, 'OK, nice, this thing is sensitive and ready to go.'

"Also, you can't pee with an erection, and the first thing you want to do in the morning is pee," he added. "So it's almost like a hindrance."

What causes morning wood?

According to New Jersey urologist Andrew Siegel, M.D., morning erections are normal and healthy.

"Most healthy men have between three and six nocturnal erections while sleeping, each lasting 10 to 15 minutes," he explained.

There are three types of erections: psychogenic, reflex and nocturnal.

"Psychogenic erections are on the basis of sights, sounds, smells or thoughts," Siegel said. "Reflex erections occur in response to direct tactile stimulation of the penis. Nocturnal erections have a unique mechanism controlled in the pons region of our brain stem and occur during rapid eye movement [REM] sleep."

During deep REM sleep, he added, your parasympathetic nervous system—the system that triggers erections—is most active.

Having to urinate may also contribute to someone experiencing morning wood.

"When the urinary bladder is full, it stimulates the same sacral nerves that are involved with penile sensation and erection," Siegel said. "Because the bladder and the penis share a common nerve supply, when the bladder is distended, an erection may occur, often referred to in slang terms as a 'piss hard-on.'"

Testosterone can also play a role as levels tend to peak in the morning and high levels of the hormone have been linked to increased numbers of nocturnal erections.

What's the point?

The purpose of nocturnal erections is unknown, but there is some speculation in medical circles.

"Current theories propose that nocturnal erections achieved during the REM phase of sleep are for the purpose of keeping penile tissues well-oxygenated and healthy," Siegel said.

As one review published in 2005 in the Journal of Sexual Medicine explained, well-oxygenated penile tissue can prevent cavernous fibrosis, the scarring of erectile tissue that can lead to erectile dysfunction (ED).

If you aren't waking up with morning erections, Michael A. Werner, M.D., a New York-based urologist, said it isn't necessarily a cause for alarm.

"Men don't always know if they have nocturnal erections because they're in response to different parts of your sleep rhythm," he said. "So you don't always wake up with them even if you had them [during the night]."

However, if a RigiScan test—which measures the quantity and rigidity of nighttime erections—reveals a scarcity or absence of quality erections, it may indicate an underlying issue.

"It tells me there's a problem with the penis—most of the time—in terms of getting and maintaining the blood," Werner explained.

"In order to get an erection, you not only have to get blood into the penis, but you also have to hold on to it," he added. "The analogy I always use is filling a bathtub: You have to fill it with water, but you also put in the stopper in order to fill up the tub. So if you're not getting nocturnal erections, then it means you're either not filling your bathtub or not holding on to the blood adequately."

What does morning wood reveal about ED?

Siegel explained, "Not being able to achieve nocturnal or morning erections are classic symptoms of erectile dysfunction."

However, it's possible to get normal and healthy morning wood but still experience erectile dysfunction in sexual situations. In some cases, this indicates a problem with getting blood into the penis fast enough.

"You have infinite time during the night to 'fill your bathtub,' even if it's flowing at a slow rate," explained Werner, hearkening back to his bathtub analogy. "It's sort of a fine point that most people miss. You can have good morning erections and good nocturnal erections but still have a problem with the blood into the penis."

Both professionals agreed that oftentimes, the problem isn't mechanical but psychological.

"If a man has intact nocturnal and a.m. erections but has ED when confronted with a sexual situation, it often indicates psychological ED or performance anxiety," Siegel said.

He recommended consulting a urologist if you are experiencing both a lack of morning erections and erectile dysfunction in sexual situations.

On the other hand, an absence of any kind of erections might merit a consultation with a cardiologist.

"Since erections are all about blood flow to the penis, intact erections are markers for cardiovascular health and their absence or diminution a clear-cut sign of perhaps a more general cardiovascular issue, a tip of the cardiovascular iceberg," Siegel said.

In some cases, fewer nocturnal erections may be linked to low testosterone. Werner said giving patients additional testosterone often restores erections, which makes his patients pretty pleased.

"What's interesting about morning erections is, as men, we are all sort of obsessed with our penises," he explained. "Even though most men don't use those morning erections for intercourse or even for masturbation, it's amazing how excited and happy they are to get them back."