Scottish girls are being asked to take part in a major research project to find out why so many are prone to developing eating disorders.

The children, aged seven to 17, will be invited to give blood samples for DNA testing as there is growing evidence that conditions such as anorexia may be genetic.

They will also be asked to keep a short food diary, answer questions about their mood, have their eye movements monitored and be weighed and measured.

For the first phase of the study - called "Girls Growing Up" - the researchers are seeking 20 girls in Glasgow, along with one of their parents, to participate. Ultimately they hope to recruit hundreds of young women across Scotland and possibly the UK.

Dr Jane Morris, a consultant psychiatrist at the Royal Cornhill Hospital, in Aberdeen, and leader of the study, said at the moment it is not clear what the different factors which contribute to eating disorders might be.

She said: "Everyone has their say and says it is fashion magazines or it is family problems and there is more and more research that comes out and shows there is a genetic background."

She hopes by recruiting enough young girls and following them up for at least five years it will be possible to identify the common factors among those who develop eating disorders and those who avoid the problem completely.

She is particularly interested in talking to the siblings of people who have suffered anorexia. "I have always had a real soft spot for the siblings of people with anorexia," she said. "Not only do they have the same genetics and the same environment, but when their sister or brother becomes ill they have the most terrible environment. They have all these stresses - we know from studies that living with a person with anorexia in a family causes even more distress and depression than living with a young person with schizophrenia...

"Yet, the majority of these kids, they not only don't get the illness - many are extraordinarily level-headed and remarkably healthy."

Why, she asked, do some girls go through puberty and exams succumb to anorexia while others don't: "What are their secrets?"

Research has already found that patients who are severely ill from an eating disorder tend to move their eyes differently from their healthy counterparts. Dr Morris said, given a picture of a face, they were more likely to focus on one small detail and then take longer to examine other parts of the image. "We still do not know if that is kind of a scar which comes from having anorexia or whether it might be in some people as a marker before it develops," she said.

This is why eye movements will be examined as part of the research. Yorkhill Children's Foundation and a charity called Millar-Mackenzie are funding the first stage, which is intended to help confirm the different information which the researchers will need to gather in order to find out how the girls differ.

Dr Harris, who is speaking about her work at the Royal Society of Edinburgh tomorrow (tue) said treatment for eating disorders tended to take a "one size fits all" approach despite the possibility of very different causal factors.

"These volunteers will definitely be contributing towards creating preventative measures against anorexia and also hopefully towards better treatment," she said.

Susan Ringwood, chief executive of eating disorders charity, Beat, said: "Eating disorders are complex psychiatric illnesses with no single cause which affect more than 1.6 million people in the UK alone. "Research is helping to show that so much more of this illness is hard wired and biological that was previously thought. "It can help people to know it isn't their fault, they didn't choose to have this problem."

A website about the Girls Growing Up study will be launched next month. Participants will be asked to attend a day's research session near the Royal Hospital for Sick Children, Yorkhill, and offered expenses as well as a gift token for their time.