True love is for 12 months only: "They say true love lasts a lifetime. But according to scientists, that intoxicating head-spinning feeling that comes when you first clap eyes on the love of your life does not last quite that long. In fact, they say the chemical in the brain which is responsible for the first flush of romance wears off after just 12 months. The researchers found the effect was the same even among couples who were still passionately in love. They studied a group of men and women aged 18 to 31, some of whom had just fallen in love, some of whom were in long-term relationships and others who were single. Among those in the first throes of passion, levels of a protein called Nerve Growth Factor - which causes those telltale palpitations, sweaty palms and butterflies - rocketed. But in couples who had been together for a year or more, the levels had fallen back to that found in singletons"