2008-02-11 06:41:37
Couples should not worry when the first flush of passion dims - scientists have
identified the hormone changes which cause the switch from lust to cuddles.
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.
Dr Petra Boynton, of the British Psychological Society, said there was a danger
people might feel they should take hormone supplements to make them feel the
initial rush of lust once more.
'Not ever-lasting'
The Italian researchers tested the levels of the hormones called neutrophins in
the blood of volunteers who were rated on a passionate love scale.
It is suggesting that what happens first is the best bit - and that isn't true
Dr Petra Boynton, British Psychological Society
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."