Causes of Morning Erections in Men

"Morning wood" is a slang term for when you awaken with an erection after sleep. It is a perfectly normal occurrence—referred to medically as nocturnal penile tumescence—in which the penis will engorge with blood during certain parts of your sleep cycle. Adolescents, teens, and young adults tend to have morning wood more than older adults.

Most morning erections tend to last for a few minutes after awakening but can persist for longer. Morning wood is not a sign of any medical or sexual problem and, despite popular belief, is not so much associated with "sex dreams" (which can cause nighttime erections and "wet dreams") as it is with REM sleep.

This article explains the causes of morning erections as well as factors that independently contribute to morning wood in people with penises.

Rapid Eye Movement

Morning erections correspond to the timing of rapid eye movement (REM) sleep. Penile erection is controlled by the autonomic nervous system. Simply put, erections in REM sleep occur when neurological stimulators increase blood flow to the penis.

Everybody has different sleep patterns, but since there are usually four or five stages of REM sleep during the night, many men have four or five erections during the night, too. Each erection can last 25 to 35 minutes, though this doesn't necessarily happen every night.

As part of normal sleep patterns, called sleep architecture, transitions occur throughout the night between the various sleep stages. People stay in REM stage sleep for longer as morning approaches, so by the time they wake they are often coming out of REM sleep. This is why men are likely to awaken in the morning with an REM sleep-related erection.

Morning erections, therefore, are secondary to the timing of REM sleep and the natural physiological processes that are associated with this sleep state in men. It seems that the body is doing what healthcare providers refer to as "testing systems" during sleep. This is a normal and healthy phenomenon in men. And the response isn't unique to men; it's also possible for the clitoris of a woman to become engorged with blood and erect during REM sleep.

Male erections typically go away within a few minutes after awakening. A persistent erection, where the blood fails to drain from an erect penis, may occur in a condition called priapism. On the other hand, a lack of morning erections may suggest a problem with the blood vessels or nerves or erectile dysfunction.

The erectile function of the penis can be tested as part of a diagnostic sleep study called a polysomnogram. However, it is not a common procedure.

Changes in Hormone Levels

Levels of testosterone, which play a role in sexual function, are higher early in the morning compared to in the afternoon or evening. This can also contribute to morning erections.

Physical Stimulation

Physical stimulation, which can occur even in a groggy, half-asleep, half-awake state, can also cause a morning erection. Even during this stage, the body can remain alert to what's going on in the environment.

Full Bladder

Men who don't get up to urinate during the night will have a full bladder in the morning. A full bladder can press on the sacral nerve, which is a group of five nerves in the lower back. This may lead to an erection.

What If Morning Erections Stop?

If you do not wake with an erection, it is not necessarily abnormal. It could be that you did not wake from REM sleep. It is also possible that the erection began to fade prior to waking completely.

In general, sleep-related erections decrease with age. But if you're not waking at least occasionally with an erection, if may be time to visit your healthcare provider for a friendly check-up.

Try to keep in mind that you're a long way from worrying about a diagnosis of erectile dysfunction. Your provider will probably want to do a full health history and eliminate other possibilities, such as obstructive sleep apnea, which is just one condition that can affect erections.

Summary

Morning erections correspond to the timing of rapid eye movement (REM) sleep. During a normal night of sleep, people usually experience about four or five stages of REM sleep, and many men have four or five erections during the night.

Although men do not always wake up at the end of each episode of REM sleep, they are likely to awaken in the morning with an REM sleep-related erection. Erections are considered a normal part of sleep physiology in men. Other causes may lead to morning erections, too, such as levels of testosterone, the presence of prolactin, the workings of the nervous system, and physical stimulation.

A Word From Verywell

You may be concerned that you're having too many or too few morning erections. Or maybe you've noticed a change in your morning "routine." If a physical matter is troubling you, you owe it to yourself and your peace of mind to make an appointment with your healthcare provider.

In the meantime, remember the tenets of living a healthy lifestyle: Eat nutritious foods, keep your weight under control for your height and age, exercise regularly, drink minimal amounts of alcohol, and avoid cigarettes.