For everything from pop music to poetry, overwhelming infatuation offers inspiration and storylines. But when might this tip over into something a little less healthy?

For months after her relationship ended, Anna* couldn’t stop thinking about him.

Each morning she’d wake with a jolt of grief; an intense, almost physical feeling that morphed into thoughts of him that consumed nearly every waking hour.

Most nights she fell asleep playing mental reruns of conversations and imagined reconciliations in her mind.

For many people, longing like this sits within the broad terrain of ordinary romantic yearning. The kind often lamented in poetry, music and film. But for Anna, what began as familiar ache slowly intensified, becoming almost unbearable.