What is 'morning wood,' and why does it happen?
“Morning wood” is a slang term that refers to a person having an erect penis when they wake up in the morning. The medical term is nocturnal penile tumescence. Some call it having a nocturnal erection.
Nocturnal penile tumescence (NPT) is not a result of sexual arousal or having a dream relating to sex. Instead, it is a normal function of the male reproductive system. In fact, regular episodes of NPT are a sign that the nerves and blood supply to the penis are healthy.
If a male does not have NPT regularly, it can indicate a health issue, such as erectile dysfunction (ED), which involves having trouble getting or keeping an erection. Not having regular NPT can also suggest other problems with the nerves or the blood supply to the male reproductive organs.
A hormonal imbalance, such as a decrease in testosterone, can also affect how often a person experiences NPT. A lack of regular NPT can sometimes result from not getting quality sleep.
As a person gets older, they can expect to experience NPT less often. This change should happen gradually, as hormone levels shift. Anyone who notices a sudden drop in the number of their NPT episodes should speak with a doctor to rule out any potential health issues.
NPT is not a typical erection because it is not related to sexual thoughts, dreams, or stimulation. It is simply a result of sleep cycles, combined with healthy nerves and blood flow in the body.
NPT tends to happen when a person is in a rapid eye movement (REM) phase of sleep. REM sleep can occur several times during an 8-hour sleep cycle. The erection may go away on its own as a person enters deeper sleep. Thus, a person may have erections several times during the night but may not be aware of them.
Often, a person wakes up at the end of a REM sleep cycle, which explains why NPT seems to happen in the morning. In addition, testosterone levels tend to be elevated in the morning. Males have high levels of this hormone, which contributes to sexual function.
An erection caused by NPT may be physically different from one caused by arousal. One study found that some men experienced pain when they had NPT, but not when they had typical erections.