“The biggest problem when you have a child with an eating disorder is this: every tactic you have ever used in parenting is useless. "Worse than that: it’s wrong,” writes journalist and author Caitlin Moran in a moving account of her daughter’s eating disorder.

It is an expression of desperation that Professor Tracey Wade understands only too well.

She has worked as a clinician in the area of eating disorders for 30 years and knows they become a family rather than an individual problem.

“We're interested in trying to get people to seek help as early as possible for an eating disorder,” Professor Wade says. “And that includes families as well as those people with an eating disorder.”

Eating disorders mainly emerge in early adolescence – although not only then – and are often dismissed at first as “a phase”. The usual trajectory is an insidious beginning, with wanting to eat a bit less, then to lose a bit of weight, then to become a vegan, then not to eat with the family. “By that time, it’s really starting to ring alarm bells,” says Professor Wade.

While intervention can seem difficult, it is essential to confront the problem early.

“Particularly when your teenage child says they want to lose weight, I think you need to really work that through with them. Do they need to lose weight? How much weight? Can we agree on a limit? So, it's actually being monitored.

But a common pattern for people with eating disorders means that once a weight goal is reached, they still don't feel that good about themselves, so they think I'll just lose a bit more weight. A vicious cycle that continues ad infinitum, even when they're at 39 kilos.”

The “crucible” for the development of most eating disorders, Professor Wade says, is at that early adolescence to mid-adolescence point, “especially if they’re in a peer group that's particularly critical of appearance and they’re being bullied or teased about appearance”.

“We also know there are character traits that predispose people, like perfectionism and high levels of anxiety. So when we talk about an eating disorder, we think that it is seen as solution to a problem – often a sense of low self-esteem and feeling a bit out of control.

“And so the focus on the weight, the number on the scales becomes very beguiling because that can be the answer to your problem.”

As to the causes, perhaps surprisingly, there is a genetic contribution to eating disorders of about 50%, only slightly lower than for schizophrenia or bipolar affective disorder.

“It's certainly higher than most people think,” says Professor Wade. “There is a bit of stigma around eating disorders, thinking that it's self-imposed or just silly girls wanting to be thin.”

But there is nothing trivial about eating disorders, which are one of the highest mortality psychiatric disorders.