Researchers from the Melbourne-based Murdoch Childrens Research Institute worked with the World Health Organisation to analyse the "disease burden" carried by people.
Using international data to calculate disease burden, scientists ranked various health conditions.
They then multiplied that figure by the number of years a person was likely to live with the disability, explained the paper's co-author Professor George Patton, from Murdoch.
They also considered years lost due to the disease, he said.
The figures, which considered millions of global participants, revealed 45 per cent of the burden among 10 to 24-year-olds could be attributed to mental disorders.
In particular depression, schizophrenia, self-harm, alcohol misuse and bipolar disorder ranked among the top 10 disability burdens.
In high-income countries, like Australia, mental illness accounted for two-thirds of the age group's disease burden.
"That's largely because we have been very successful in dealing with other causes of disease burden (like HIV and tuberculosis)," Prof Patton told AAP.
"(Locally) the disease burden is driven by conditions causing disability rather than death."
The study, the first to analyse the global causes of disability in adolescence, could be used to identify risk factors for disease later in life, researchers said.
"Although the lifestyles that young people adopt might not have an immediate effect on their health, they have substantial effects later in life," Prof Patton said.
"Interventions to address health risk behaviours and unhealthy lifestyles are likely to be more effective in these years than in adulthood when patterns are established."
Also contributing to the disease burden of 10 to 24-year-olds were unintentional injuries (12 per cent) and infectious diseases(10 per cent).
The burden of disease increased steadily with age, Prof Patton said.
Rates were fairly equal between men and women, although after the age of 25, burden soared among males and continued to do so into old age.
© 2011 AAP