By Brandon Peters, MD Updated on March 23, 2023
Medically reviewed by Jamin Brahmbhatt, MD
This article is a repost which originally appeared on verywell health
Edited for content. The opinions expressed in this article may not reflect the opinions of this site’s editors, staff or members.
Key Points
‧ Morning erections are not necessarily associated with sex dreams.
‧ During sleep, REM sleep cycles affect erectile activity.
‧ Subtle contact of the penis with bedsheets can induce erections.
“Morning wood” is when the penis engorges with blood and you wake up with an erection. This is a perfectly normal occurrence. Most morning erections tend to last for a few minutes after awakening but can persist for longer.
Despite what some think, these erections are not so much associated with “sex dreams” as they are certain parts of the sleep cycle—namely, REM sleep.1 Changes in hormone levels, a full bladder, and even physical stimulation from a bedsheet can also cause morning wood.
This article explains the causes of morning erections, clinically known as nocturnal penile tumescence. It also reviews factors that independently contribute to morning wood in people with penises.
Erections and Your Sleep Cycle
Morning erections correspond to the timing of rapid eye movement (REM) sleep. Because REM sleep effects neurological stimulators that increase blood flow to the penis, penile erection is more likely during this part of the sleep cycle.1
Everybody has different sleep patterns. But since there are usually four or five stages of REM sleep during the night, people with penises may 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.
People stay in REM stage sleep for longer as morning approaches. By the time they wake, they are often still coming out of REM sleep. This is why you may experience morning wood, which typically subsides within a few minutes of awakening.
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 people with penises. In fact, it can also happen in those without them: The clitoris can become engorged with blood and erect during REM sleep as well.
Hormones Levels in the Morning
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.
Even Subtle Touch Can Cause Erections
Physical touching 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.
Effect of a 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.
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, stimulation of the nerve from a full bladder can cause an erection.
Morning erections can be a reassuring sign that your nerves, blood supply, and circulation are healthy.
What If Morning Erections Stop or I Never Have Them?
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 check-up.
Adolescents, teens, and young adults tend to have morning wood more often than older adults.
A complete lack of morning erections may suggest a problem with the blood vessels or nerves. It can also indicate erectile dysfunction, a common condition in which a person is unable to get or keep an erection firm enough for satisfactory sexual intercourse.
See your healthcare provider. They 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. A diagnostic sleep study called a polysomnogram may be recommended.
What If a Morning Erection Doesn’t Go Away?
Persistent erections may occur in a condition called priapism. With this uncommon condition, either blood flow through the penis is not as it should be (nonischemic or high-flow priapism) or blood gets trapped in the penis after it becomes erect (ischemic or low-flow priapism).
Priapism can result in erections that last hours. With nonischemic cases, the shaft of the penis may lose some rigidity and you likely won’t experience pain. With ischemic priapism, the shaft is rigid, the tip is soft, and there is pain that worsens with time.
Give the erection some time to resolve. If it goes away, but long-lasting and/or painful erections keep happening, see your healthcare provider.
If your erection lasts for more than four hours, go to the emergency room.
Summary
Morning erections correspond to the timing of rapid eye movement (REM) sleep, which you may still be coming out of when you wake up. They can also be caused by hormone fluctuations, a full bladder, and subtle touch.
These erections typically resolve within minutes of you waking up.
Morning wood is not only common, but normal. If you don’t ever experience these erections, they stop, or they last several hours, see a healthcare provider.
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Youn G. Why do healthy men experience morning erections? Open Psychol J. 2017;10(1). doi:10.2174/1874350101710010049
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
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
Boston University School of Medicine. The central mechanisms of sexual function.
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