Sex influences our brain activity in ways that may impact our emotions, sensitivity to pain, and even sleep.
Sexual intercourse is known to impact the way in which the rest of our body functions.
Recent studies have shown that it can have an effect on how much we eat, and how well the heart functions.
Also, a study published in the Journal of Health and Social Behavior in 2016 found that women who have satisfying sex later in life might be better protected against the risk of high blood pressure.
Many of the effects of sex on the body are actually tied to the way in which this pastime influences brain activity and the release of hormones in the central nervous system.
Here, we explain what happens in the brain when we are sexually stimulated, and we look at how this activity can lead to changes in mood, metabolism, and the perception of pain.
Brain activity and sexual stimulation
For both men and women, sexual stimulation and satisfaction have been demonstrated to increase the activity of brain networks related to pain and emotional states, as well as to the reward system.
This led some researchers to liken sex to other stimulants from which we expect an instant "high," such as drugs and alcohol.
The brain and penile stimulation
A 2005 study by researchers at the University Medical Center Groningen in the Netherlands used positron emission tomography scans to monitor the cerebral blood flow of male participants while their genitals were being stimulated by their female partners.
The scans demonstrated that stimulating the erect penis increased blood flow in the posterior insula and the secondary somatosensory cortex in the right hemisphere of the brain, while decreasing it in the right amygdala.
The insula is a part of the brain that has been tied to processing emotions, as well as to sensations of pain and warmth. Similarly, the secondary somatosensory cortex is thought to play an important role in encoding sensations of pain.
An older study from the same university — which focused on brain regions that were activated at the time of ejaculation — found that there was an increase in blood flow to the cerebellum, which also plays a key role in the processing of emotions.
The researchers liken the activation of the cerebellum during ejaculation to the pleasure rush caused by other activities that stimulate the brain's reward system.
"Our results correspond with reports of cerebellar activation during heroin rush, sexual arousal, listening to pleasurable music, and monetary reward."
The brain and the female orgasm
In a study of the female orgasm that was conducted last year, scientists from Rutgers University in Newark, NJ, monitored the brain activity of 10 female participants as they achieved the peak of their pleasure — either by self-stimulation or by being stimulated by their partners.
The regions that were "significantly activated" during orgasm, the team found, included part of the prefrontal cortex, the orbitofrontal cortex, the insula, the cingulate gyrus, and the cerebellum.
These brain regions are variously involved in the processing of emotions and sensations of pain, as well as in the regulation of some metabolic processes and decision-making.
Another study previously covered on MNT suggested that the rhythmic and pleasurable stimulation associated with orgasm puts the brain in a trance-like state. Study author Adam Safron compares the effect of female orgasms on the brain to that induced by dancing or listening to music.
"Music and dance may be the only things that come close to sexual interaction in their power to entrain neural rhythms and produce sensory absorption and trance," he writes.
"That is," he adds, "the reasons we enjoy sexual experiences may overlap heavily with the reasons we enjoy musical experience, both in terms of proximate (i.e. neural entrainment and induction of trance-like states) and ultimate (i.e. mate choice and bonding) levels of causation."
Sex and hormonal activity
So what does this all mean? In essence, it means that sex can impact our mood — normally for the better, but sometimes for the worse.
Having sex releases a lot of hormones linked to emotions. This usually bodes well for our mood, but there are some exceptions.
Having sex has repeatedly been associated with improved moods and psychological, as well as physiological, relaxation.
The reason behind why we may feel that stress impacts us less after a session between the sheets is due to a brain region called the hypothalamus.
Higher levels of oxytocin can make us feel more relaxed, as studies have noted that it can offset the effects of cortisol, the hormone linked with an increased state of stress.
Not only does oxytocin make us calmer, but it also dampens our sense of pain. A study from 2013 found that this hormone could relieve headaches in individuals living with them as a chronic condition.
Can sex also make us feel down?
The answer to that, unfortunately, is "yes." While sex is generally hailed as a great natural remedy for the blues, a small segment of the population actually report an instant down rather than an instant high after engaging in this activity.
This condition is known as "postcoital dysphoria," and its causes remain largely unknown. One study conducted in 2010 interviewed 222 female university students to better understand its effects.
Of these participants, 32.9 percent said that they had experienced negative moods after sex.
The team noted that a lifelong prevalence of this condition could be down to past traumatic events. In most cases, however, its causes remained unclear and a biological predisposition could not be eliminated.
"This draws attention to the unique nature of [postcoital dysphoria], where the melancholy is limited only to the period following sexual intercourse and the individual cannot explain why the dysphoria occurs," the authors write.
Sex may lead to better sleep
Researchers from Central Queensland University in Australia also hypothesized that the release of oxytocin during sex may act as a sedative, leading to a better night's sleep.
In sleep, the prefrontal cortex exhibits the slowest brainwave activity compared with other brain regions, which supports the proper execution of cognitive functions during the daytime.
Researchers say that sex may lead to better cognitive functioning in older age, protecting people from memory loss and other cognitive impairments. Studies have shown that "older men who are sexually active [...] have increased levels of general cognitive function."
For women, being sexually active later in life appears to sustain memory recall, specifically. These effects may be due to the action of hormones such as testosterone and oxytocin, which are influenced by intercourse.
So, next time you're about to slip between the sheets with that special someone, just know that this moment of passion will spark a whole neural firework show, releasing a special hormonal cocktail that will, at its best, charge a whole set of biological batteries.