Morning glory, morning tent, boner, how many other terms are there for this often misunderstood phenomenon? Morning wood is one slang term for the erections that men wake up with; the medical term for these erections is “nocturnal penile tumescence”.


What causes erections?

An erection is a response to a combination of factors involving the nervous system and the endocrine system. When sexually aroused, a message from the brain sends chemical messages to the nerve endings in the penis which in turn causes blood to flow into the penis. Muscles in the penis then contract to trap the blood which results in an erection.


Erections while we sleep

Erections occur during the rapid eye movement (REM) stage of sleep and it is not clearly understood what causes a man to have erections during sleep although it is thought that increased activity of the parasympathetic during REM sleep may be involved.

Some people think that there is a function to nighttime erections and that is to keep your erectile function healthy by keeping the erectile tissue in good shape for when you need it during waking hours.

Another function may also be to indicate that the bladder is full. This argument is strengthened by the fact that as soon as the bladder is emptied on waking the erection will subside.

Typically the last period of REM occurs before waking and as a result men will often wake with an erection.


Typical morning erections

Morning erections are a normal part of male life and although male babies can have erections, morning erections tend to occur with increasing size, rigidity and frequency as puberty progresses. For adult men, they are a frequent occurrence.


What causes morning erections?

There are theories as to what causes men to have nighttime and therefore morning erections. It is most likely that they are caused by a number of factors but the theories are as follows:

  • Physical stimulation caused by a partner’s touch to the genitals (this may be accidental) may cause a man to have an erection even if his eyes are closed.

  • Hormones may play a part and testosterone levels are at their highest in the body immediately after waking from the REM stage of sleep. This increased level of the hormone may be sufficient to cause an erection despite there being no visual or physical stimulation. One augment behind this is that as men get older natural levels of testosterone begin to drop and in men aged 40 – 50 years, the incidence of nocturnal penile tumescence starts to decrease.


Brain relaxation

When a man is awake, his body releases hormones to suppress erections and this theory explore the idea that the brain ‘relaxes’ and releases less of those suppressive hormones during the night which in turn allows the erections to occur.

In fact, according to which publication we choose to read the ‘causes’ or nocturnal erections are different. The only thing that we are sure of is that they happen when the erectile function is healthy.


Morning erections and erectile dysfunction

Morning erections are likely to reduce in frequency as a man gets older and this needs to be taken into account; the absence of morning erections can however be a sign of erectile dysfunction or ‘the inability to achieve or sustain an erection long enough for the purpose of having sexual intercourse’.

Erectile dysfunction can be an early indicator of an underlying disease such as cardiovascular disease or diabetes and so a lack of ‘dawn horns’ may suggest that it is time to visit the doctor for a check-up. Other causes of erectile dysfunction can include:

  • Heart disease
  • Atherosclerosis
  • High blood pressure (hypertension)
  • High levels of cholesterol
  • Obesity
  • Lack of regular exercise
  • Parkinson's disease
  • Multiple sclerosis
  • Peyronie’s disease
  • Smoking
  • Alcohol abuse
  • Sleep disorders
  • Some prescription medication as well as some illegal drugs

It can be a problem to decide what is the ‘norm’ when it comes to the frequency of morning erections.



At the end of the day, although some people may find it a nuisance (especially if they sleep on their front) it is a good indicator of normal, healthy blood supply to the genital area.

If you find that you are getting fewer morning erections or no morning erections at all it is probably time to discuss things with your healthcare professional. They can check for more life-threatening conditions such as diabetes as well as giving advice on lifestyle issues. 

There are many treatments available for both underlying conditions and erectile dysfunction so help is out there!