Cases of anorexia are on the rise among preteen children in the UK and Ireland, research suggests, with rates having as much as doubled in 10 years.

The study, which looked at cases of anorexia diagnosed by psychiatrists in hospitals or specialist clinics, estimates that 3.2 per 100,000 children aged between eight and 12 met criteria for anorexia for the first time in 2015, compared with 1.5 to 2.1 per 100,000 in 2006. Trends for older children could not be examined due to lack to comparable historical data.

The research follows reports of a doubling in hospital admissions for eating disorders in the past six years, with the surge driven by an uptick in cases among teenage girls and women in their early 20s.

Sarah Byford, a professor of health economics at King’s College London and co-author of the new study, said those potentially vulnerable to developing an eating disorder may be being exposed to risk factors at an earlier age, including pressure to diet or do well at school.

Alternatively, she said, the figures may be a positive story: “This finding might simply be that we are getting better at identifying young people [with anorexia],” she said.

Tom Quinn, of the eating disorder charity Beat, also urged further research into the trend, and said health service providers should ensure they were making the most of the available resources.

“Since 2016, substantial extra funding has been made available to the NHS in England for investment in specialist eating disorder services for under 18s, but not all commissioners and providers have prioritised these services sufficiently,” he said.

To conduct the study, published in the journal BMJ Open, Byford and colleagues asked all child and adolescent consultant psychiatrists based in hospitals, universities or community settings in the UK and Ireland to report the number of anorexia cases they had seen every month from February to September 2015.

If a clinician reported a case, they were subsequently asked to fill in a questionnaire to allow the team to gather details of the patient and their diagnosis.

Over the eight-month period, 305 cases were reported that met requirements for the study, with the vast majority in girls and people of white ethnicity.

To calculate the rate of new cases of anorexia, the team took into account that only half of clinicians responded and others did not complete the questionnaire.

The results suggest that among children aged eight to 17 years old, there are 13.7 new cases of anorexia per 100,000 people per year. Among girls the estimate was higher, at 25.7 per 100,000, with the age of diagnosis peaking at 15 years old.

The team then focused on eight- to 12-year-olds, finding a marked increase in cases in recent years.

But Byford said it was important to look at the figures in context. “For the younger children aged eight to 12 we are only talking maybe 250 [new cases a year],” she said.

Byford said that both the latest figures and earlier estimates probably underestimated the true incidence of anorexia, pointing out that many do not seek help, while older teenagers may go to adult services. The Royal College of Psychiatrists has said that fewer than a quarter of people with eating disorders in the UK receive treatment.

Dr Agnes Ayton, chair of the eating disorders faculty at the Royal College of Psychiatrists, said “This study shows what psychiatrists have been seeing every day, which is a worrying rise in the number of young people suffering from the most deadly mental illness. The causes are complex, and much more research needs to be done in order to better support those affected. Anecdotally, reasons could include increasing pressures on children in schools, and advertisements encouraging unrealistic ideas of body image.”

Quinn also said the figures were probably underestimates, and urged further research into earlier interventions. “Full recovery from an eating disorder is possible and the sooner someone gets the treatment they need, the more likely they are to make a full and sustained recovery,” he said.