Health Guide delivered to your inbox

You can unsubscribe at any time.
Please review our privacy policy for more info.

Last updated January 16, 2020. 5 minute read

What causes morning wood? Why do guys get it?

Men slip into REM sleep about an hour and a half after dozing off. Each episode of REM sleep corresponds with an erection lasting 20 to 25 minutes. Men typically have five erections during an eight-hour sleep cycle. The last of them is often referred to as “morning wood.”

Written by Health Guide
Reviewed by Dr. Mike Bohl, MD, MPH

Do guys really get erections in their sleep?

Yes, men get erections while they sleep. In fact, on average, most guys get five erections every single night.

Moreover, men are supposed to wake up with an erection every morning. Seriously, if you’re in “good health,” your body is hard-wired for “morning wood.” Nocturnal erections—also known as “sleep-related erections” (SREs) or “nocturnal penile tumescence” (NPT)—and morning erections are so normal that their presence (or absence) can be an important indicator of a man’s overall health. 

If you don’t regularly wake up with that familiar morning erection, it could indicate that your testosterone levels, blood flow, or something more serious is off.

Vitals

  • Morning erections are an important indicator of your overall health.
  • Men typically have five nocturnal erections during an eight-hour sleep cycle, with each erection lasting about 25 minutes.
  • Erectile dysfunction could indicate a number of underlying health problems.
  • If you aren’t getting morning erections, consult a healthcare provider.

Morning erections over the millennia

Nocturnal erections are part of being male—and they start young. Healthcare providers have noted erections in fetuses during ultrasounds, and even young boys experience erections throughout childhood long before the onset of puberty. The penis is a prominent organ. The fact that it swells during the night (and each morning) isn’t new information. 

In fact, researchers reviewing old medical texts and scientific data and theological records (even the Church tracked erections) published their findings on the history of nocturnal erections in a paper titled “Sleep-Related Erections Throughout the Ages” (Van Driel, 2014). The authors noted that the ability to achieve an erection during sleep was such a “reliable indicator of virility” that erectile dysfunction (ED) was grounds for divorce.

According to ecclesiastical records, a jury would actually stay by the bedside of an accused man and wait for him to get an erection in his sleep. As early as 1920, Wilhelm Stekel, Freud’s contemporary and in many ways his equal, noted that a morning erection (a.k.a. the last Sleep-Related Erection (SRE) of the night) is a “[n]aturally occurring phenomenon in healthy men from infancy to old age.”

Advertisement

ED treatments, prescribed online

A real, U.S.-licensed physician will review your information and get back to you within 24 hours.

Learn more

Why do men get nocturnal erections?

While there’s no shortage of evidence for the existence of morning and nocturnal erections, nobody knows the exact reasons for morning erections. Here’s what we do know about erections and sleep. 

Men typically have five nocturnal erections during an eight-hour sleep cycle (Youn, 2017), with each erection lasting about 25 minutes. That’s about one erection every 90 minutes. It didn’t take long for researchers to note that this pattern was strikingly similar to another 90-minute cycle that occurs during sleep—REM (rapid eye movement) phase sleep. 

Pay attention to your morning wood. The loss of that familiar morning erection could be the first sign of a significant problem. If you aren’t getting morning erections, see a healthcare provider.

Erections and REM sleep

In 1965, researchers confirmed the relationship between REM sleep and nocturnal erections, or the dreaming phase of sleep, fueling several decades of speculation about what really occurs during REM sleep to cause erections. Essentially, men slip into REM sleep about an hour and a half after dozing off. Each episode of REM sleep corresponds with an erection lasting 20 to 25 minutes. Men typically have five erections during an eight-hour sleep cycle.

What’s interesting is that each nocturnal erection lasts longer as the night progresses—just as the REM phases lengthen (Fisher, 1965). The association is that tightly linked. Despite this strong correlation and the fact that men spend nearly 25% of their sleep cycle with an erection, we still don’t honestly know why morning wood happens. But we have some ideas.

Nocturnal erections: competing theories

A leading theory is that norepinephrine production slows down during REM sleep (Mitchell, 2010). This is the chemical primarily responsible for keeping the penis relaxed. Basically, the part of the brain that maintains norepinephrine levels gets turned down during REM sleep. This lets the testosterone-related excitatory mechanisms take over, leading to an erection.

Another theory is that your body produces more nitric oxide during REM sleep. Nitric oxide is responsible for making the blood vessels of the penis relax, allowing all the extra blood needed to cause an erection to enter the penis. 

The bottom line is that no one really knows what role REM sleep plays in nocturnal penile tumescence. Why do men get nighttime erections (many times) a night? Are morning wood and REM sleep linked, or is it just a really interesting coincidence? There are a lot of theories.

Why is morning wood so important?

So many things have to go right for you to achieve a strong erection.

You have to release hormones on-demand and dilate arteries to carry blood to the penis. Your nervous system has to transmit signals perfectly, and your mind has to be in harmony with your body. There’s a lot that can go wrong. If you’re having difficulty getting erections, it could be due to any number of serious health risks. 

The blood vessels of the penis are also small compared to other areas of the body. That means other underlying conditions can show up first as ED. Erectile dysfunction could indicate high cholesterol levels, stress, type 2 diabetes (or prediabetes), hypertension (high blood pressure), depression, sleep disorders, heart disease, hormone issues, side effects of medication, consequences of lifestyle choices, emotional issues, or more.

“If I could only ask a man one question to assess his health, it would be, ‘Do you wake up with an erection?’” – Dr. Steven Lamm

Erectile dysfunction and health issues

In a 2005 study titled “Erectile Dysfunction and Subsequent Cardiovascular Disease,” researchers followed men ages 40–70 years old for seven years to see if men with ED were more likely to develop a cardiac condition than those without ED. The results of this long-term study concluded that “[o]lder men in this group have a 2x greater risk of cardiovascular disease than men without erectile dysfunction” (Thompson, 2005).

The study went on to say: “This analysis suggests that the initial presentation of a man with erectile dysfunction should prompt the evaluating physician to screen for standard cardiovascular risk factors.”

Erectile dysfunction affects men of all ages

Erectile dysfunction isn’t just a problem for older guys. An increasing number of young men are diagnosed with ED every year. One Italian study from 2013, reported a dramatic uptick in new cases of erectile dysfunction in young men. In fact, the study found that in 439 men with erectile dysfunction, 114 (26%) were under 40 (mean age 32). Worse, nearly half of them had “severe ED” (Capogrosso, 2013). 

Another Swiss study found that “around 30% of young men experienced erectile dysfunction.” The study concluded: “Multiple health-compromising factors are associated with [ED],” and ED should act as a “red flag for health professionals to encourage them to take any opportunity to talk about sexuality with their young male patients.” 

Morning erections are vital to your health

One ED study from 2016 just straight out states the importance of erections right in the title: “Erectile Dysfunction In Young Patients Is a Proxy of Overall Men’s Health Status” (Capogrosso, 2016). Pay attention to your morning wood. The loss of that familiar morning erection could be the first sign of a significant problem. If you aren’t getting morning erections, see a healthcare provider.