It is not the most conventional way of dealing with infertility, marriage difficulties and a midlife crisis. But Susan Shapiro's decision to track down her old flames propelled her towards a state of happiness and marital bliss that those on Prozac or in therapy can only dream about.

Reacquainting herself with her 'exes' also resulted in a best-selling memoir - Five Men Who Broke My Heart - that is enjoying huge success in America as devotees take their own trips down lost love's memory lane.

'If you're single and jobless and your ex is happily married and successful, you might not be in the best place to do this,' Shapiro said recently in an interview on NBC's Today show.

'And if you're bitter or if you think, "this guy's a jerk, he screwed me over", I'd say you shouldn't. But if you're open-minded and want to learn some things about yourself you might not want to hear, then I'd strongly recommend catching up with the ones you've loved and lost.'

The most important lessons the New York writer learnt was that she hadn't been ready to get married until she was 35, and that she had depended too much on men and love for happiness.

She also discovered that in several cases her perception of why the relationship had failed differed from her former partners' views about what went wrong.

The journey was inspired when, six months before her fortieth birthday, Shapiro's longest-lasting former boyfriend - with whom she had a 15-year on-off relationship - contacted her to ask if she would write about his new book.

His timing couldn't have been worse. That morning Shapiro had received two faxes, one from her gynaecologist explaining that her husband's low sperm count was responsible for their failure to conceive, the other from her agent, telling her that five publishers had rejected the novel she had spent five years writing.

She interviewed her ex, but spent most of the time talking about what went wrong with their relationship. 'I always thought he was the one who ruined everything,' said Shapiro. 'I played the victim, the guys were always the cads.

'But it was very weird and illuminating to hear his perspective. It made me realise that I was turned on by male unavailability. If he'd ever said to me, "let's get married and have babies," I'd have bolted.'

Only her first love refused to meet her. 'I'd rather take out my own appendix with a bottle of Jack and a dull spoon,' said his email.

The heady allure of contacting past lovers has already been experienced in the UK through the Friends Reunited. Its message board is dotted with accounts from people whose spouses have left them for old flames or who have themselves rekindled an old romance.

Therapists who have examined the Friends Reunited phenomenon say the pull of an old relationship, particularly a first love, can be overwhelming, especially to those who feel unhappy, unloved, or just suffused with boredom in their middle-aged marriages.

Facing the person who broke your heart can be empowering, according to Susan Quilliam, a leading relationship psychologist. 'I think it can be a great idea. We need to get closure on things and we need to learn from things and very often when a relationship splits up we do neither. You never really say goodbye and you never really find out what happened. You never have the time to mourn because you're too busy thinking: "I need to meet someone else," or saying he or she is a complete bastard. Meeting up with old flames gives both parties the chance to learn lessons and to say all the things they've always wanted to say, then to draw a line under it and move on.'

Christine Northam, a Relate counsellor, says it is normal and healthy in midlife to reflect on the past and the paths you didn't take. However, she has some reservations: 'I would be concerned if someone wanted to go back because they had a shred of hope that they might rekindle the relationship. If someone has the courage to do it to enhance their self-awareness, great. But if they want that relationship back, you'd have to ask why they haven't moved on.'

'My lost love... yet I only felt indifference'

The last thing I expected to feel, when I was reunited with my first love, who had left me broken-hearted, was nothing.

Here was the man I had planned to marry, to have children with, grow old with, cycle round the world with. Here was the man who had written songs about the depth of his love for me. Here was the man who, after eight years of first love's impassioned blindness, informed me at 4am on January 4, 1996, that he was leaving me.

I wailed as he unburdened himself of the details of his year-long affair. She was a young blonde he's met after a gig and they were head over heels. With the sheer pointlessness and horror of existence without him yawning before me like a grave, I crawled into bed, put a Teenage Fanclub CD on repeat and remained there for a few years.

I have often wondered how I would react if I met him now. I have rehearsed all the terrible things I would say as he lay in hospital stricken with something terminal.

I have also imagined how sweet it would be if, when I bumped into him, I was with a perfect specimen of a husband and our four beautiful children, while he was fat, bald, ravaged by wild regret and very much alone. Other times, I've dreamed of falling in love with him all over again.

Instead, when I met him, all I felt, apart from very nervous, was indifference. There was no anger, rage, hatred. But nor was there any real sadness or attraction.

The following day he sent me a very long email, saying he looked back on the 1987 to 1995 period of his life as a 'golden time' and apologised 'from the bottom of his heart'. He signed off by suggesting that he probably both enriched and fucked up my life. He fucked up a few years but in the process did me a huge favour.

He said he felt depressed after meeting me because it brought back too many troubling and painful memories that he preferred to keep in a box.

I felt on top of the world after meeting him because I never thought the day would come when I would sit across from my first love, who left me broken hearted, and want to thank him.