Anatomy

What causes morning wood?

Morning wood, or as it’s formally known, nocturnal penile tumescence (NPT), is a common occurrence for many boys and men. From time to time, men may wake up with an erect penis. This is most common in younger men, although men of all ages may experience NPT. The cause of NPT is likely multifactorial. Doctors have a few theories that help explain why men wake up with an erect penis from time to time, but none of these theories are supported by concrete, medical evidence. These theories include: Physical stimulation Though your eyes are shut, your body is still very much aware of what’s happening around you. If you or your partner accidentally touch or graze your genitals, you may become erect. Your body senses the stimulation and responds with an erection. Hormone shifts Your testosterone level is at its highest in the morning after you wake up. It is highest immediately after waking up from rapid eye movement (REM) sleep stage. The increase in this hormone alone may be enough to cause an erection, even in the absence of any physical stimulation. As men get older, usually between ages 40 and 50, natural testosterone levels begin to fall. As this level decreases, episodes of NPT may decrease as well. Brain relaxation During your waking hours, your body releases hormones to suppress erections. When you’re asleep, your body releases less of those hormones. Combine this fact with the other reasons you may experience an erection in your sleep, and NPT becomes more likely. What’s clearer is what doesn’t cause morning wood. For example, needing to urinate isn’t responsible for morning wood. Some people believe a morning erection keeps them from urinating during their sleep, but this is not true. Morning wood also isn’t always a sign of sexual stimulation. In many cases, NPT isn’t caused by dreams or thoughts of a sexual nature.