Why Do Healthy Men Experience Morning Erections?

Gahyun Youn*
Department of Psychology, Chonnam National University, 77 Yongbong-Ro, Gwangju 61186, Korea

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© 2017 Gahyun Youn.

open-access license: This is an open access article distributed under the terms of the Creative Commons Attribution 4.0 International Public License (CC-BY 4.0), a copy of which is available at: ( This license permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

* Address correspondence to this author at the Department of Psychology, Chonnam National University, 77 Yongbong-Ro, Gwangju 61186, Korea; Tel: +82 62-530-2655, +82 10 6612-2655; Fax: +82 62 530-2659; Emails:,


People begin the sleep cycle with a period of non-rapid eye movement (NREM) sleep, followed by a very short period of rapid eye movement (REM) sleep. During a normal night of sleep, humans usually experience about four or five periods of REM sleep. Penile erections have generally been considered to be an epiphenomenon of REM sleep-related physiological changes for healthy males. Thus, men are very likely to awaken in the morning with a REM sleep-related erection, which is also known as nocturnal penile tumescence (NPT). Men who are physically under great strain or serious psychological stress may find it difficult to maintain a psychogenic erection. The best time for them to have sex would be during sleep time, such as when they are experiencing REM sleep-related erections. It is reasonable to assume that the NPT phenomena might have evolved as a tool for having sex, in the context of both procreation and recreation.

Keywords : REM sleep, Morning erection, Nocturnal penile tumescence, Sexual intercourse, Procreation, Recreational sex.