A team from the University of Pisa in Italy found the bodily chemistry which makes people sexually attractive to new partners lasts, at most, two years.
When couples move into a “stable relationship” phase, other hormones take over, Chemistry World reports.
But one psychologist warned the hormone shift is wrongly seen as negative.
Levels of these chemical messengers were much higher in those who were in the early stages of romance.
Testosterone was also found to increase in love-struck women, but to reduce in men when they are in love.
But in people who had been with their partners for between one and two years these so-called “love molecules” had gone, even though the relationship had survived.
The scientists found that the lust molecule was replaced by the so-called “cuddle hormone” – oxytocin – in couples who had been together for several years.
Oxytocin, is a chemical that induces labour and milk-production in new and pregnant mothers.
Donatella Marazziti, who led the research team, said: “If lovers swear their feelings to be ever-lasting, the hormones tell a different story.”
Similar research conducted by Enzo Emanuele at the University of Pavia found that levels of a chemical messenger called nerve growth factor (NGF) increased with romantic intensity.
After one to two years, NGF levels had reduced to normal.
‘Real Cupid’s arrows’
The researchers said: “Whether more nerve growth is needed in the early stage of romance because of all the new experiences that are engraved into the brain, or whether it has a second, as yet unknown function in the chemistry of love, remains to be explored.”
Michael Gross, a bio-chemist and science writer who has studied the latest findings, said: “It shows that different hormones are present in the blood when people are acutely in love while there is no evidence of the same hormones in people who have been in a stable relationship for many years.
“In fact the love molecules can disappear as early as 12 months after a relationship has started to be replaced by another chemical glue that keeps couples together.”
He added: “To any romantically inclined chemist, it should be deeply satisfying to be able to prove that chemical messengers communicate romantic feeling between humans.”
“It may be the only thing that science can offer as a real-world analogy to Cupid’s arrows.”
But Dr Boynton said: “This feeds into a 1970s view that when you meet it’s all sparky, and then it’s a downward trajectory to cuddles – which is seen as a negative.
“It is suggesting that what happens first is the best bit – and that isn’t true.”
She added: “I’m concerned that, having identified these hormones, there will be some move to suggest replacements to recreate the early passion.”
Full article: http://news.bbc.co.uk/2/hi/health/4669104.stm
Photo: BBC News
2- Cupid’s chemistry (Chemistry World – 2006)
Molecules in love
Donatella Marazziti, a psychiatrist at the University of Pisa, Italy, started out investigating the hormonal changes connected to obsessive-compulsive disorder, before moving on to those that occur when people fall in love. Initially, she and her co-workers found a decrease in functionality of serotonin transporters in the blood of enamoured volunteers, who had been selected and rated on a passionate love scale (PLS), much like those in the US studies. Like obsessive-compulsive patients, the love-struck volunteers showed a reduced concentration of serotonin in the blood, which might explain why early phase romantic love can turn into obsession.
In her most recent study, Marazitti, together with fellow Pisa researcher Domenico Canale, casts the net wider to check for changes in the concentration of a number of hormones, including oestradiol, progesterone, dehydroepiandrosterone, and androstenedione, which were found to be unaffected by any romantic feelings. In contrast, they observed changes for cortisol, follicle stimulating hormone, and testosterone. Some effects were gender-specific. For example, testosterone was found to increase in love-struck women but to reduce in men when they are in love.
If lovers swear their feelings to be everlasting, the hormones clearly tell a different story. Re-testing the same subjects 12-24 months later, Marazziti and Canale found that the hormonal differences had disappeared entirely, even if the relationships remained intact.
Using the same method for volunteer selection, Enzo Emanuele and his co-workers at the University of Pavia, Italy, investigated whether a different class of chemical messengers, the neurotrophins, is involved in the romantic experience. At the end of 2005 they reported that the concentration of nerve growth factor (NGF) in the blood exceeds normal levels in enamoured volunteers, and that it increases with the intensity of romantic feelings as measured by the PLS. Whether more NGF is needed in early stage romance because of all the new experiences that are engraved into the brain, or whether it has a second, as yet unknown, function in the chemistry of love remains to be explored.
Emanuele and co-workers also found that after one to two years, all of the love molecules had gone, even if the relationship survived. Neither the initial intensity of the PLS nor the concentration of NGF appeared to be a suitable predictor for the fate of the relationship after that period.
But, if all the chemical messengers of intensive romantic feelings disappear within two years, what is the chemical glue that keeps – at least some – couples together?
A key molecule for the attachment phase is the hormone oxytocin, a nonapeptide that was first described as the chemical that induces labour and lactation, but later found a second job as the human ‘cuddle hormone’. It is related to the hormone vasopressin, which controls kidney function, and has also been identified when prairie voles form attachments.
Experiments have shown that, depending on the species, either or both of these hormones can make animals snuggle up. In humans, it has been shown that oxytocin production is high during female orgasm. Apart from that, and its role in childbirth, very little was known about oxytocin’s role in human physiology and psychology until recently.
Last year, several groups reported progress in investigating oxytocin’s role in humans, linking the hormone to early socialisation, social cognition, and trust. Michael Kosfeld and his co-workers at the University of Zurich, Switzerland, showed that applying oxytocin via a nasal spray made participants in a trust game more trusting towards other human participants, but not towards a computer. This finding fits in with the expectations of the Italian researchers. ‘I am not surprised by the results of Kosfeld’s paper,’ says Donatella Marazziti, who has just completed a study of oxytocin in romantic love but keeps the details under wraps.
Finally, another family of chemical messengers associated with love, the pheromones, are equally poorly understood in humans, as most of our knowledge derives from animals. By definition, pheromones are chemicals intended for communication between individuals of the same species. Their use in insects is well understood to the extent that pheromone traps are commercially available for crop protection.
Our knowledge is much more incomplete for mammals, let alone humans. Most people’s educated guess is that pheromones secreted from some glands, eg with sweat, are recognised by receptors presumably located in a very small part of our nose known as Jacobson’s organ or vomero-nasal organ (VNO). However, it was only in 2002 that researchers could pin down some putative mammalian pheromone receptors in mice.
Last October, Hiroko Kimoto’s group at the University of Tokyo, Japan, added a surprising piece to the jigsaw. The researchers showed that a non-volatile mouse pheromone, which they called ESP-1 (exocrine-gland secreting peptide) is released from the tear glands of the male mouse and, after face to face contact, activates receptors in the female’s VNO.
Again, it remains unclear whether human male tears have a similar effect on the female of the species. Indeed, there is a long-running controversy as to whether the human VNO is in fact a working part of our physiology or whether it’s an inactive relic of mammalian evolution. It now appears that the evidence is slowly giving the pro-VNO party the upper hand.
Full article: http://www.rsc.org/chemistryworld/Issues/2006/February/CupidChemistry.asp
3- The Royal Society of Chemistry Guide to Love – 2008
A Chemistry World story on the chemistry of love has resurfaced after two years, as one of the most emailed BBC news stories.
The heightened interest in the story headlined Sex Chemistry ‘lasts two years’ is presumably down to the approach of Valentine’s Day.
The article explains why lovers’ early passions subside when their ‘lust molecules’ fade; however it is replaced by another molecule which has been linked to a longer-lasting bond.
Is there more to love and life than chemistry? The RSC explains:
Whether you are looking to tempt a future partner, ward off unwanted Valentine advances or simply get through the day, it all comes down to chemistry.
The romantics of us may want to believe that love really is a mystery of the soul.
The science shows that the mystery is perhaps not so profound.
Let the RSC explain the real chemistry behind the warm and tender feeling that love is meant to bring. If you don’t want your romantic notion to be contaminated with a cocktail of chemicals, then look away now…
The excitement and feeling of love is a cascade of chemical signals speeding rapidly through the brain to trigger electrical or chemical effects. Via nerve cells, these are then involved with controlling what we perceive as emotional reactions.
We are then unable to control some of the familiar effects such as racing heartbeat, sweaty palms and breathing heavily.
PEA-Phenylethylamine (or “jubilation”)
This fishy-smelling hormone, often found to be low in depressive people, is similar to adrenaline. It is linked to pulse rates, and is significantly higher after physical activity. Research shows this may be the trigger for “romantic love”, and may lead to sweaty hands, lumps in the throat and butterflies in the stomach.
But after 2-3 years the nerve endings in the brain will have adapted to the increased levels of PEA and the excitation sadly fades.
This chemical may also explain the high divorce rates which peak close to the forth year of marriage.
This drug can be found in chocolate and almonds, but unfortunately may be rapidly metabolised before significant quantities can reach the brain.
Oxytocin (the “cuddle” hormone)
Not only can we blame the physical responses of lust and the honeymoon period of love on chemicals. Chemistry is also responsible for the perhaps less tangible desire for tenderness, comfort and physical and mental closeness.
The hormone oxytocin is responsible for these emotional feelings; it has also been associated with maternal behaviour, trust and generosity.
Levels of oxytocin soar with a tender touch, sexual arousal and after orgasm, creating a feeling of safety and comfort and increasing the bond between couples after an amorous encounter.
The more intimate encounters you have with one partner, the more you associate the pleasant feeling oxytocin brings with that person. This chemical is the long-term glue of relationships. However an overdose of this glue might manifest as an infatuation or obsessive dependence.
Serotonin ( the ‘happiness’ chemical), chase away the winter blues by eating chocolate
This chemical mainly affects the brain and about 10 milligrams are needed for psychic stability. Lack of serotonin leads to lack of drive, sleep disorder, anxiety and depression. Serotonin can be provided by foods such as bananas, pineapple, strawberries, raspberries, sesame, rice pudding and chocolate.
Studies have also shown that levels of serotonin in the brain depend on our exposure to light. So rather than wallowing alone in a dark room this Valentine’s, indulge in a massive rice pudding smothered in strawberries and chocolate to get you through.
“Don’t wash, Will arrive in Three days” a private message from Napoleon Bonaparte to his wife-
Experiments have shown that attraction between two people is crucially influenced by body odours and pheromones- love will only work if noses agree.
Scientists claim we are more likely to be attracted to the smell from someone with a different genetic make-up to our own, and repelled by the odour of someone who is genetically similar. If in doubt whether you want the attention, have a good scrub or douse yourself with garlic!
Full article: http://www.rsc.org/AboutUs/News/PressReleases/2008/LoveAndChemistry.asp
Photo: Chemistry World