Absence makes the heart grow fonder. All you need is love. It’s better to have loved and lost than never to have loved at all.

If cliches and pop songs are anything to go by, humans spend a substantial portion of waking and sleeping hours thinking and dreaming about the pursuit of love – in all its many forms.

But is love all pink hearts, roses and teddy bears – or is there a darker side? Can love, or the absence of love, generate a form of sickness? Can it even lead to lasting physical or mental illness? And is it possible to die of a broken heart?

Love can hurt. Ian McEwan framed a pathological form of affection, leading to obsession in his 1997 novel “Enduring Love”. The central character, Joe, is stalked and harassed by the mentally unwell Jed, following a tragic accident that unites them both.

The condition that McEwan explores so vividly is erotomania, which was described by de Clerembault in 1942, and the syndrome still bears his name today. It describes the delusional but unwavering belief of being secretly but nonetheless intensely loved by another person.

De Clerembault was not the first person to notice these symptoms. They appear even in the words of Hippocrates, described as a form of unrequited........

© The Conversation