Humans spend an inordinate amount of time thinking about, pursuing, and having sex. It's not just about making babies, because people have sex long before and after they have children - if they have them at all.
Whatever the reason, if you're having frequent sex, you're likely to see some benefits. Not only is it good for your mental wellbeing, it will probably have a positive impact on your general health too.
Several studies over the years have shown the effects of having sex. Here are 14 of the main findings so far.
Endorphins are the body's natural painkillers. During sex, endorphins flood the body and brain, easing any discomfort. For some people, it can cure a headache. This may be due to endorphins, or the release of the neurotransmitter serotonin, which makes you feel happy.
Sex isn't as good as other forms of exercise, but it certainly does burn a fair few calories. One study from the University of Montreal looked at how many calories couples burned during sex. During a 30-minute session, men burned an average of 101 calories, while women burned 69. That was about 4.2 calories or 3.1 calories per minute respectively.
A study published in the journal Psychology Report found students who had sex at least once a week had higher levels of a certain antibody which is vital for fighting off illnesses. In fact, the levels were 30% higher than in those who had no sex at all.
According to the NHS, anything that exercises the heart is good for you, and that includes sex. But the benefits depend on how rigorous you're doing it. On average, the peak heart rate during sex is about the same as walking up a flight of stairs, and the recommendation is to workout moderately for about 150 minutes a week.
As well as all the feel-good chemicals your brain releases during sex, you also have a decrease in cortisol. Research has shown how penetrative sex helps people cope the best with stress, but all kinds help people relax.
A study published in the BMJ in 2004 found that frequent ejaculations appear to be linked to a decreased risk of prostate cancer. Out of 50,000 males aged between 40 and 75, men who reported 21 or more a month were less likely to get prostate cancer than those who reported four to seven. A follow-up study replicated the results.
Sex can also boost your sense of wellbeing. According to a study of 3,000 Americans aged 57 to 85, people who were having sex rated their general health higher than those who weren't getting any. Love was also linked with people saying they were in "excellent" health rather than "good" or "poor" health.
A happy marriage has been shown to reduce the risk of angina (a heart condition) and stomach ulcers in men, according to research. In one study of 10,000 men, those who felt "loved and supported" had a lower risk of angina.In another study of 8,000 men, those who had problems at home had more of a chance of developing a duodenal ulcer. Sex isn't the only way to show love and affection, but it's certainly one.
People who embrace each other frequently will probably have lower blood pressure, according to a study from 2003. Couples who held each other's hands for 10 minutes then hugged for 20 seconds weren't as worked up about stress from activities like public speaking.
As previously discussed, sex is exercise, so it's normal to feel tired after it. But the release of oxytocin also helps you feel sleepy. For men in particular, an orgasm reduces activity in the prefrontal cortex of the brain, which is really important for getting a good night's sleep. A study, reported by the Mail online, showed how the blood rush after climax depletes muscles of energy-producing glycogen - exhausting you further.
In 2005, research from the University Medical Center Groningen found how sex can help men get in touch with their emotions. Men were hooked up to brain scans to monitor their cerebral blood flow while their female partners stimulated them. The results showed that blood flow was increased to the the posterior insula, and decreased to the right amygdala. The insula is an area that has been linked to processing emotions, pain, and warmth.
Sex can improve people's performance in short-term memory tests, according to a study from earlier this year. Some researchers conclude it is because sex boosts brain cell growth in areas of the brain associated with memory, while others suggest it's because of the sexual "afterglow" that pumps us full of dopamine and oxytocin. There is a growing body of research that shows how sex improves brain power.
Blood flow decreases to the amygdala during sex - the area of the brain linked to anxiety disorders. A lot of blood flowing to the amygdala may increase the chance of developing an anxiety disorder or other mental health problems, so sex might be one way to reduce that risk.
In a study published in Psychoneuroendocrinology, more sexual intimacy was linked to longer telomeres (part of our chromosomes that protect them from damage).
The results showed a correlation, not a causation, so it could simply be that healthier people have more sex, rather than sex being good for genes.
For people who are single or celibate, hanging out with friends is great for your health too. One study of 1,500 people over 70 years old found those who had strong friendships lived longer. It could be because friends have a positive impact on our health and lifestyle choices, or simply because they are there for emotional support.