Causes of Morning Erections in Men

"Morning wood" is when the penis engorges with blood and you wake up with an erection. Clinically known as nocturnal penile tumescence, it is a perfectly normal occurrence. Despite what some think, morning wood is not so much associated with "sex dreams" as it is with certain parts of the sleep cycle—namely, REM sleep.

Most morning erections tend to last for a few minutes after awakening but can persist for longer. This is not a sign of any medical or sexual problem. Adolescents, teens, and young adults tend to have morning wood more than older adults.

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

What Causes Morning Erections
Verywell / Brianna Gilmartin

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.

ED Is Very Common

 Erectile dysfunction—a condition in which a man is unable to get or keep an erection firm enough for satisfactory sexual intercourse—is very common among men. However, it is not a normal part of aging.

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

The sex hormone testosterone plays a central role in the sexual functions of people with penises. Research has shown that testosterone helps facilitate nearly every facet of an erection, from the activation of nerves that stimulate smooth muscles of the penis to the engorgement of blood in the spongy interior of the penis.

Testosterone levels also fluctuate and tend to be higher early in the morning than in the afternoon or evening. This incidental increase can also be one of the contributing factors to a morning erection.

Physical Stimulation

Physical stimulation of the penis can, on its own, cause an erection in the absence of sexual stimulation. Research has shown that physical stimulation sends sensory signals directly to the lower part of the spinal cord which functions at the body's "erection center."

Even when half-asleep or half-awake, these sensory nerves can be alert to even subtle changes in the environment. As such, the tactile sensation of a bedsheet or pajama fabric against the penis may be enough to provoke a morning erection.

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.

Your nervous system helps keep your body running while you sleep. Because the sacral nerve is responsible for erections while you're asleep or half-asleep, morning erections can be a reassuring sign that your nerves, blood supply, and circulation are healthy.

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 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.

8 Sources
Verywell Health uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
  1. Youn G. Why do healthy men experience morning erections? Open Psychol J. 2017;10(1). doi:10.2174/1874350101710010049

  2. Anele UA, Morrison BF, Burnett AL. Molecular pathophysiology of priapism: Emerging targets. Curr Drug Targets. 2015;16(5):474-83. doi:10.2174/1389450115666141111111842.

  3. Franjić S. Male sexual dysfunction. J Androl Gynaecol. 2019;7(1):3.

  4. U.S. Department of Health and Human Services. National Institutes of Health. National Institute of Diabetes and Digestive and Kidney Diseases. Definition & facts for erectile dysfunction.

  5. Isidoria AM, Buvat J, Corona G, et al. A critical analysis of the role of testosterone in erectile function: from pathophysiology to treatment—a systematic review. Eur Urol. 2014 Jan;65(1):99-112. doi:10.1016/j.eururo.2013.08.048

  6. Crawford ED, Poage W, Nyhuis A, et al. Measurement of testosterone: how important is a morning blood draw? Curr Med Res Opin. 2015;31(10):1911-4. doi: 10.1185/03007995.2015.1082994

  7. Boston University School of Medicine. The central mechanisms of sexual function.

  8. Leungwattanakij S. Erectile dysfunction. Bangkok Med J. 2016;11:57-. doi:10.31524/bkkmedj.2016.02.012

By Brandon Peters, MD
Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist.