Kerre McIvor recalls the exact moment she realised she was invisible. Walking down the street on a wintry afternoon, she noticed not a single passing man bothered to so much as glance her way.
"They didn't see me," she says. "They stepped round me as if I were a lamppost. I'd been consigned to the ranks of the invisible women. It was a slap in the face."
Everyone knows about the male mid-life crisis - the sudden yearning for a sports car, a leather jacket, a younger wife. But in her latest book, McIvor lifts the lid on a newly discovered phenomenon: the female mid-life funk. And she admits to suffering a serious bout.
"It's been tough," she says. "I've always bounced along through life and this sort of snuck up on me.
"It was a combination of things. The decline of my body, the grey hairs I found in my eyebrows, not having the same stamina I used to, the sheer misery of being a responsible adult. I was sick of paying bills and turning up to work on time. I wanted to run away and regain my lost youth."
She admits to a phase of wanting to "play Russian roulette" with her life, but husband Tom refused to fall in with her madcap plans to chuck in their jobs and head off for an adventure.
In her book Musings From Middle Age, Kerre Woodham (she wasn't married when she wrote it so used her maiden name) describes the struggle with depression and dissatisfaction that culminated in a couple of sessions with a counsellor.
"She suggested I jot down the times when I felt happy or sad and the catalyst for those times. It really did help. I'd never really thought about the triggers for the emotions I felt."
The Herald on Sunday columnist's treatise on middle age resonates with her trademark humour but holds a serious message, too. For women's mid-life years are when fertility declines, kids leave home and beauty tends to fade.
According to research from Cornell University, 36.1 per cent of women report a difficult mid-life transition as opposed to 34 per cent of men. And at the UK's Warwick University they've devised what they call the theory of U-shaped happiness - essentially, we are happy when we are young; happiness declines to its lowest point in the mid-40s for men and women, then starts to rise again in older age.
In her book, McIvor, 48, points a finger at female celebrities such as Nicole Kidman, blaming them for holding women to an unrealistic ideal of how they should be in middle age. "It's totally misleading the way they all look smooth-faced."
She admits to having had a hit of Botox herself, but only in her frown lines.
She certainly has no plans to go with the alternative to invisibility. "Turn cougar? God no. Even if I wasn't married I wouldn't be into rogering younger guys to feel like I was young and groovy," she laughs.
"I intend to hit 50 with quiet dignity in two years' time."