A nocturnal emission, informally known as a wet dream or sex dream or sleep orgasm, is a spontaneous orgasm during sleep that includes ejaculation for a male, or vaginal wetness or an orgasm (or both) for a female. Nocturnal emissions are most common during adolescence and early young adult years, but they may happen any time after puberty. It is possible for men to wake up during a wet dream or simply to sleep through it, but for women, some researchers have added the requirement that she should also awaken during the orgasm and perceive that the orgasm happened before it counts as a wet dream. Vaginal lubrication alone does not mean that the woman has had an orgasm.
Due to the difficulty in collecting ejaculate produced during nocturnal emissions, relatively few studies have examined its composition. In the largest study, which included nocturnal emission samples from 10 men with idiopathic anejaculation, the semen concentration was equivalent to samples obtained from the same men by penile vibratory stimulation, although the proportions of sperm which were mobile and which were of normal morphology were higher in the nocturnal emission specimens.
In a detailed study, men and women reported that approximately 8% of their everyday dreams contain some form of sexual-related activity. Four percent of sex dreams among both men and women resulted in orgasms.
The frequency of nocturnal emissions is highly variable. Some reported that it is due to being sexually inactive for a period of 1–2 weeks, with no engagement in either intercourse or masturbation. Some males have experienced large numbers of nocturnal emissions as teenagers, while others have never experienced one. In the U.S., 83% of men experience nocturnal emissions at some time in their life. For males who have experienced nocturnal emissions, the mean frequency ranges from 0.36 times per week (about once every three weeks) for single 15-year-old males to 0.18 times per week (about once every five-and-a-half weeks) for 40-year-old single males. For married males, the mean ranges from 0.23 times per week (about once per month) for 19-year-old married males to 0.15 times per week (about once every two months) for 50-year-old married males. In some parts of the world, nocturnal emissions are more common. For example, in Indonesia surveys have shown that 97% of men experience nocturnal emissions by the age of 24.
Some males have the emissions only at a certain age, while others have them throughout their lives following puberty. The frequency with which one has nocturnal emissions has not been conclusively linked to frequency of masturbation. Alfred Kinsey found there may be "some correlation between the frequencies of masturbation and the frequencies of nocturnal emissions. In general the males who have the highest frequencies of nocturnal emissions may have somewhat lower rates of masturbation."
One factor that can affect the number of nocturnal emissions males have is whether they take testosterone-based drugs. In a 1998 study by Finkelstein et al, the number of boys reporting nocturnal emissions drastically increased as their testosterone doses were increased, from 17% of subjects with no treatment to 90% of subjects at a high dose.
Thirteen percent of males experience their first ejaculation as a result of a nocturnal emission. Kinsey found that males experiencing their first ejaculation through a nocturnal emission were older than those experiencing their first ejaculation by means of masturbation. The study indicates that such a first ejaculation resulting from a nocturnal emission was delayed a year or more from what would have been developmentally possible for such males through physical stimulation.
The frequency of nocturnal emissions is variable, just as with males. In 1953, sex researcher Alfred Kinsey found that nearly 40% of the women he interviewed have had one or more nocturnal orgasms or wet dreams. Those who reported experiencing these said that they usually had them several times a year and that they first occurred as early as thirteen, and usually by the age of 21. Kinsey defined female nocturnal orgasm as sexual arousal during sleep that awakens one to perceive the experience of orgasm.
Research published by Barbara L Wells in the 1986 Journal of Sex indicates that as many as 85% of women have experienced nocturnal orgasm by the age of 21. This research was based on women waking up with/during orgasm.
Studies have found that more males have more frequent spontaneous nocturnal sexual experiences than females. Female wet dreams may be more difficult to identify with certainty than male wet dreams because ejaculation is usually associated with male orgasm while vaginal lubrication may not indicate orgasm.
Sexual activity is a commonly reported theme of lucid dreams. LaBerge, Greenleaf, and Kedzierski (1983) undertook a pilot study to determine the extent to which subjectively experienced sexual activity during REM lucid dreaming would be reflected in physiological responses:
Since women report more orgasms in dreams than men do, we began with a female subject. We recorded many different aspects of her physiology that would normally be affected by sexual arousal, including respiration, heart rate, vaginal muscle tone, and vaginal pulse amplitude. The experiment called for her to make specific eye movement signals at the following points: when she realized she is dreaming, when she began sexual activity (in the dream), and when she experienced orgasm. She reported a lucid dream in which she carried out the experimental task exactly as agreed upon. Our analysis revealed significant correspondences between the dream activities she reported and all but one of the physiological measures. During the fifteen-second section of her physiological record which she signaled as the moment of orgasm, her vaginal muscle activity, vaginal pulse amplitude, and respiration rate reached their highest values of the night, and they also were considerably elevated in comparison to the rest of the REM period. Contrary to expectation, heart rate increased only slightly.— LaBerge, S., Greenleaf, W., & Kedzierski, B. (1983). Physiological responses to dreamed sexual activity during lucid REM sleep. Psychophysiology, 20, 454-455.
There are numerous cultural and religious views on nocturnal emissions. Below is a limited summary of some perspectives.
... Again, those males
Into the surging channels of whose years
Now first has passed the seed (engendered
Within their members by the ripened days)
Are in their sleep confronted from without
By idol-images of some fair form—
Tidings of glorious face and lovely bloom,
Which stir and goad the regions turgid now
With seed abundant; so that, as it were
With all the matter acted duly out,
They pour the billows of a potent stream
And stain their garment.
If a man has an emission of semen, he shall bathe his whole body in water and be unclean [Hebrew tameh] until the evening. And every garment and every skin on which the semen comes shall be washed with water and be unclean until the evening.
When you are encamped against your enemies, then you shall keep yourself from every evil thing. If any man among you becomes unclean [Hebrew lo yihyeh tahor, literally 'will not be clean'] because of a nocturnal emission [literally: 'by reason of what happens to him by night'], then he shall go outside the camp. He shall not come inside the camp, but when evening comes, he shall bathe himself in water, and as the sun sets, he may come inside the camp.
A third passage relates more specifically to priests, requiring any "of the offspring of Aaron who has ... a discharge", among other causes of ritual defilement, to abstain from eating holy offerings until after a ritual immersion in a mikveh and until the subsequent night-fall.
Saint Augustine held that male nocturnal emissions, unlike masturbation, did not pollute the conscience of a man, because they were not voluntary carnal acts, and were therefore not to be considered a sin.
A wet dream is not a sin in Islam. Moreover, whereas a person fasting (in Ramadan or otherwise) would normally be considered to have broken their fast by ejaculating on purpose (during either masturbation or intercourse), nocturnal emission is not such a cause. They are still required to bathe prior to undergoing some rituals in the religion.
Muslim scholars consider ejaculation something that makes one temporarily ritually impure, a condition known as junub; meaning that a Muslim who has had an orgasm or ejaculated must have a ghusl (consisting of ablution followed by bathing the entire body so that not a single hair remains dry on the whole body — may also require one to rub the body according to Maliki school of thought, dalk in Arabic — while showering) before they can read any verse of the Qur'an or perform the formal prayers. Informal supplications and prayers (du'a) do not require such a bath.
In European folklore, nocturnal emissions were believed to be caused by a succubus copulating with the individual at night, an event associated with sleep paralysis and possibly night terrors.