Urological Health Penis Health Causes of Morning Erections in Men By Brandon Peters, MD facebook twitter Brandon Peters, MD, is a board-certified neurologist and sleep medicine specialist. Learn about our editorial process Brandon Peters, MD Medically reviewed by Medically reviewed by Jamin Brahmbhatt, MD on August 27, 2020 facebook linkedin Jamin Brahmbhatt, MD, is a board-certified urologist and Chief of Surgery at Orlando Health South Lake Hospital. Learn about our Medical Review Board Jamin Brahmbhatt, MD on August 27, 2020 Print Table of Contents View All Table of Contents Role of Sleep Stage Timing of Erections in Sleep Absence of Morning Erections Men often wake up with an erection first thing in the morning, but what causes morning wood or morning erections? Learn about this phenomenon, why it is associated with REM sleep, and what it might mean if it doesn't occur. Verywell / Brianna Gilmartin Morning Erections and the Role of Sleep Stage Morning erections might actually relate to the timing of rapid eye movement (REM) sleep. As part of normal sleep patterns, called sleep architecture, transitions occur throughout the night between the various sleep stages. As morning approaches, you'll stay in REM stage sleep for longer. When you first wake up, you are often coming out of REM sleep. In addition to the vivid movie-like dreams that are characteristic of REM sleep, the penis also becomes erect and engorged with blood during these periods. This is due to the activity of the parasympathetic nervous system affecting the sacral nerve. When this occurs in the morning, the stiffened penis may be referred to in slang terms as "morning wood" or "morning glory." Therefore, morning erections 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 testing systems during sleep, and this is a normal and healthy phenomenon in men. It may even be noted in young children. It is also possible for the clitoris of a woman to become engorged with blood and erect during REM sleep. These 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. A lack of morning erections may suggest a problem with the blood vessels, nerves, or erectile dysfunction. Find out If Not Having a Morning Erection Means Erectile Dysfunction The Normal Timing of Erections in Sleep REM sleep periods occur starting 80 to 110 minutes into sleep and may occur at this interval periodically three to four times throughout the sleep period. As noted, REM sleep becomes more prolonged towards morning. Therefore, more REM sleep and more erections occur towards morning. The precise timing of these erections may be difficult to predict as there is quite a bit of variability. The length of time from the onset of the erection, with a 2 mm change in the circumference of the penis, to a full erection is usually 10 minutes. The erection may last up to 25 minutes. Though not routinely performed, the erectile function of the penis can be tested as part of a diagnostic sleep study called a polysomnogram. What If Morning Erections Do Not Occur? If you do not wake with an erection, it is not necessarily abnormal. It may be that you did not wake from REM sleep. It is also possible that the erection began to fade prior to waking completely. For those who frequently wake with a morning erection, rest assured that this is a normal part of sleep. In general, sleep-related erections decrease with age. This may correlate with impotence that occurs during the daytime. In contrast, the presence of erections in sleep when daytime impotence occurs may suggest non-physiological causes of the difficulty maintaining an erection (such as stress or performance anxiety). Interestingly, untreated obstructive sleep apnea may also decrease erections. No matter the cause, if you have problems maintaining an erection, speak with your doctor about treatment options. Was this page helpful? Thanks for your feedback! Sign up for our Health Tip of the Day newsletter, and receive daily tips that will help you live your healthiest life. Sign Up You're in! Thank you, {{form.email}}, for signing up. There was an error. Please try again. What are your concerns? Other Inaccurate Hard to Understand Submit Article 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. Anele UA, Morrison BF, Burnett AL. Molecular pathophysiology of priapism: emerging targets. Curr Drug Targets. 2015;16(5):474-83. doi:10.2174/1389450115666141111111842 Peever J, Fuller PM. The Biology of REM Sleep. Curr Biol. 2017;27(22):R1237-R1248. doi:10.1016/j.cub.2017.10.026 Additional Reading Why Do Men Get Morning Erections? 5 Answers to Your Questions. Cleveland Clinic. https://health.clevelandclinic.org/2016/06/men-get-morning-erections-5-answers-questions/ . Kryger MH, Roth T, Dement WC. Principles and Practice of Sleep Medicine. Philadelphia, PA: Elsevier; 2017.