One in three first-year university-level students report symptoms of a mental health disorder, according to a new international study.

The study investigated the prevalence of psychological disorders – including major depression, mania, generalised anxiety disorder, panic disorder, alcohol use disorder and substance use disorder – among freshers in eight different industrialised countries.

The findings, part of a World Health Organization initiative, are based on a series of web-based health surveys given to students within a few months of starting university-level education.

35% of the 13,984 students who completed the questionnaire reported having suffered from at least one of the disorders at some point during their life, while 31% reported having suffered from them over the 12-month period prior to taking the survey.

Major depression was the most common disorder, followed by anxiety, and the median age of onset for the disorders was just 14.2 years of age.

“The transition from high school or secondary school to college or university can be really challenging,” said Randy Auerbach, who studies depression and suicide at Columbia University and is the lead author on the paper, which questioned students in Australia, Belgium, Germany, Mexico, Northern Ireland, South Africa, Spain and the US.

“The rates of the disorders are alarmingly high,” he said, adding that the findings point to “an enormous public health problem”.

The true prevalence may be far higher that captured in the study, because the scientists focused only on the most common disorders.

“We found that these disorders are broadly distributed across the student population, which suggests to us mainly that we need to be doing more to better understand mental disorders on college campuses,” said Auerbach.

Being female, being older or having a non-heterosexual identification were “modestly related” with a higher prevalence of the disorders, but further research is needed before calling for particular interventions for these groups of people, said Auerbach. “That’s a story that remains to be written,” he cautioned.

David Gunnell, an epidemiologist and public health physician at the University of Bristol, welcomed the findings and their potential application in developing interventions: “It’s a really important study. It highlights the high levels of mental health problems among students once they come to university in those different countries.

“It’s interesting to note that many of these first-year students were arriving with pre-existing problems.”

The findings, which are published in the Journal of Abnormal Psychology, are particularly troubling given the the high prevalence of suicide among adolescents and young adults in the UK.

Suicide is the main cause of death in people under 35, with more than 1,600 cases in the UK every year.

According to data from the Office of National Statistics, there has been an increase in suicide rates among 15- to 19-year-olds in the UK in the last five or six years, but rates are not yet as high as they were in the 1980s. Gunnell said: “The number of student suicides have also increased during this same period, but the absolute rate of suicides amongst students, the number of deaths per 100,000 students, is less than half that of the wider population.

“So while there’s a concern in rise in student suicides, perhaps there’s a greater concern in the rise in suicides among young people. They appear to be at greater risk than students.”

Researchers in the UK, speaking at a media briefing on student suicide on Thursday, called for more research to be carried out before evidence-based policies can be developed.

“We need a lot more research to try and understand the sort of problems that lead to suicide,” said Keith Hawton, director of the Centre for Suicide Research at the University of Oxford, who also called for unbiased, sensitive and balanced reporting of the topic in the media.

This need for research was also echoed by Auerbach, who stressed the need to develop more innovative ways to reach students who may not be accessing typical services in counselling centres on campuses.

Online treatment could be an alternative outlet for students that would allow for “more immediate access to care and in a way that is scalable, relatively inexpensive and can work around their schedule, addressing some concerns that they may have around stigma,” he said.

• In the UK, the Samaritans can be contacted on 116 123. In the US, the National Suicide Prevention Hotline is 1-800-273-8255. In Australia, the crisis support service Lifeline is on 13 11 14. Hotlines in other countries can be found here.