Depression is the main cause of disability and illness in young people aged between 10 and 19 worldwide, while self-harm is the fifth main cause, according to a major new report by the World Health Organization (WHO).

The findings are based on consultations with children and teenagers worldwide, as well as published evidence on this issue.

The report, Health for the World's Adolescents, reveals that around 1.3 million teenagers died in 2012 and the top three causes of death globally are road traffic accidents, HIV/AIDS and suicide.

"The world has not paid enough attention to the health of adolescents. We hope this report will focus high-level attention on the health needs of 10 to 19-year-olds and serve as a springboard for accelerated action on adolescent health," commented Dr Flavia Bustreo of the WHO.

According to the report, road traffic injuries are the biggest cause of teen deaths worldwide and the second biggest cause of disability and illness. Boys are disproportionately affected - they are three times more likely than girls to die in road accidents.

Depression meanwhile is the main cause of disability and illness and suicide is the third main cause of death among teenagers. The report points out that some studies indicate that half of all people who develop mental health difficulties display their first symptoms by the age of 14.

HIV is the second main cause of death among teenagers worldwide. The report points out that while HIV-related deaths are falling in all other population groups, they appear to be rising among teenagers. This has mainly been seen in Africa.

The report also looked at health behaviours and found that less than one in four teenagers are getting enough exercise and in some countries, around one-third of teenagers are already obese.

"If left unchecked, health problems and behaviours that arise during adolescence - such as tobacco and alcohol use, diet and exercise patterns, overweight and obesity - have a serious impact on the health and development of adolescents today, and potentially devastating effects on their health as adults tomorrow," commented the report's lead author, Jane Ferguson, a scientist in the WHO's Department of Maternal, Newborn, Child and Adolescent Health.

The top five causes of death among teenagers worldwide are road traffic accidents, HIV/AIDS, suicide, lower respiratory infections and violence. The top five causes of disability and illness are depression, road traffic accidents, anaemia, HIV/AIDS and self-harm.

For more information on depression, see our Depression Clinic here