More than one in five young people in the developed world drop out of high school, which leads to a higher risk of unemployment, ill health and crime.

The study in the Journal of Economic Psychology examined data from the US National Longitudinal Study of Adolescents to Adult Health, a nationally representative sample of 90,000 students in grades 7 to 12 at 132 schools.

The authors, Dr Eugenio Zucchelli and Dr Giuseppe Migali, from Lancaster University said : "Forgone healthcare is a consistently significant predictor" and could be used to identify teenagers at risk of leaving before the age of 18.

Over a third of dropouts do not seek healthcare when needed compared with only over a quarter of other high school students. 

Not using healthcare includes not choosing to access healthcare for reasons including "did not know who to see" and "I thought the problem will go away"; this was used as a marker of the ability to assess the long-term consequences of actions.

The researchers excluded teenagers who could not pay or did not have transport to visit the doctor and the ones with chronic conditions.

A risky attitude towards health is also common among more than half of dropouts, who are more likely to smoke, drink and take drugs. 

High school graduates and dropouts differ on the Big Five personality traits used by psychologists.

Dropouts are more likely to have combinations of the following traits: 

* low conscientiousness 
* neuroticism 
* introversion

Researchers say "Individuals who forgo their healthcare and present low conscientiousness and introversion have the highest risk of dropout."