Penile erection - on waking?
What is the cause of erection in males first thing in the morning?
It is normal for men to have erections during sleep. Penile erections can be considered to be a normal physiological component of REM (rapid eye movement) sleep, which is that particular phase of sleep when dreaming occurs. Erections can occur while dreaming, irrespective of the content of the dream. Most REM sleep occurs in the early morning therefore it is quite likely that a man will waken soon after a period of REM if not actually waking up directly from REM sleep. Therefore the chances are that a man is likely to waken with an erection if he has just been through a period of REM sleep.