“Yet there are a heap of people who have some symptoms but don’t meet the criteria, but who appear to be just as at-risk as those who meet the criteria. They’re at later risk of depression and anxiety disorders and suicidal behaviours to the same extent that those meeting the criteria are.”

So, the outlook grows worse. Fergusson estimates that by adding those whose symptoms may currently lie below the radar but who will develop depression, its prevalence would rise by 20 to 30 percent. That is, the current figure of about seven percent who meet the criteria each year could rise to nine or 10 percent. Over a lifetime, that translates into 30 to 40 percent of the population who will, at some time, develop a depressive disorder. The present estimate is about 20 percent.

The prospects are especially bad for women. In this country, the accepted ratio is two women with depression to every man. Researcher Janet Carter believes that the gender ratio is being squashed as increasing numbers of men become more open to treatment, especially for mild depression.

Many men simply put up with it: “They’re pushing along through life rather than embracing it and some people just think that’s the way it is,” says Carter. “They come in because they’ve got anger problems and they’re reluctant to come in the first place. Then you tell them they’re depressed. That can be quite difficult for some men to get their heads around.”

But, in the meantime, the numbers remain stacked against women.

Marina McCartney should have nothing at all to be depressed about. She is young, beautiful, talented, enterprising. She is a leading model.

Back in 1997, she was 20. And she was Miss New Zealand.

But McCartney was a different beauty queen. She was one of 11 children in a poor family from Mangere. Her catwalk campaign was funded on nothing. She planned to take on the world’s beauty queens in the Miss Universe contest on what she could borrow or beg, until the Holmes show started its own campaign and got her the money.

Right in the middle of all that excitement, she was struck by depression.

From this distance, it might be understandable. “I was naive and I was dealing with a life entirely different from my own,” she says. “It was very superficial. Fashion, beauty, money – they’re circles of the least substance, I think. I didn’t understand that world.

“When you’re a beauty queen, people like to think you’re stupid, or arrogant. At one function, a girl was laughing hysterically, ‘Oh my god, a real live Barbie doll.’ It taught me a lot about human nature. I come from a family that concentrated on education. I was deputy head girl at my school, I was a nerd, and all of a sudden I was in a world that was the opposite.

“It was the most amazing time of my life and the hardest, a weird mix.”

She didn’t recognise her depression at first. “I saw it as failure,” she says. “But as soon as I realised there was a label for what was happening to me, it made it a lot easier. That’s the start of recovery.”