Image copyright Thinkstock Image caption Children are safer, but are more likely to stay inside playing on a computer

Young people in the United States are safer than in the 1970s or 1990s, according to a long-term study.

Duke University's Child Well-Being Index has been recording the state of childhood in the US since 1975.

Children and teenagers are less likely to be victims of violent crime, while risky behaviours like binge drinking and smoking cigarettes are in decline.

But researchers say safer lives could also reflect the fact children spend much more time indoors.

This could also be linked to another big trend, the rise in childhood obesity, now almost four times more prevalent than in the 1970s.

Safer but overweight

Researchers say the reduction in physical danger has followed a trend for young people to spend more time at home playing computer games or using laptops or mobile phones.

The rising health threat is now from so many children becoming overweight.

The Index, which draws upon official data from sources like the US Department of Justice, the Census Bureau, the US Department of Education, the National Center for Education Statistics and the National Center for Health Statistics, shows the likelihood of a teenager becoming the victim of violent crime is now lower than in 1994 and considerably lower than in 1975.

Image copyright Thinkstock Image caption Sands of time: Children are less likely to face violence or early death than the 1970s

Despite high-profile concerns about safety, researchers say children are now at lower risk of violence and much less likely to die before reaching adulthood.

The level of "violent crime victimisation" up to the age of 19 climbed through the 1980s, peaked in the mid-1990s and then fell sharply, reaching its lowest point in 2010. It has risen again since, but remains below the average for the four decades.

The death rate among young people up to the age of 19 has fallen to about a third of mid-1970s levels.

And over the past 20 years, teenagers have become less likely to smoke tobacco or to binge drink alcohol. In contrast, the use of illicit drugs, mostly cannabis, has remained more constant.

About a quarter of 17- to 18-year-olds reported having used drugs in the previous month, a level similar to the late 1990s.

This is still considerably below levels of youth drug use in the late 1970s and early 1980s, says the study, which also uses the Monitoring the Future research, which has tracked the behaviour of 50,000 young people each year since the 1970s.

The Index, produced each year, notes a "slight improvement" in the state of children's lives in the US.

Incomes squeezed

Family incomes have risen slightly, but the impact of the recession is still apparent, with typical family income below late 1990s levels.

The long-term figures show the pressure on family incomes in recent decades. The current typical income of families with children, when inflation is taken into account, is only 11% higher than in 1975.

Image copyright Thinkstock Image caption Teenage birth rates have fallen to levels lower than the 1970s

The figures on education also show only modest increases in levels of qualifications, during decades when many other countries experienced much greater improvements.

The study also suggests many big changes in family structure and beliefs took place between the mid-1970s and the late-1980s, while the past 20 years has shown a more stable picture.

The proportion of children living in single-parent families rose sharply in the 1970s and 1980s. But the current levels, with about a quarter of children in single-parent families, are similar to 20 years ago.

Young people's attendance at religious services has also remained broadly similar after a big decline in the 1970s and early 1980s. The current attendance rate of more than 30% is similar to late 1980s levels.

The teenage birth rate is now at its lowest since this index was launched in 1975. It peaked in the early 1990s and has fallen each year since. The proportion of 15- to 17-year-old girls giving birth is now about a third of 1975 numbers.

The report concludes that, apart from rising levels of obesity, the short-term picture for young people's well-being is positive, with even greater improvements over the longer term.

"Compared to 20 years ago, U.S. children are doing pretty well," said Kenneth Laud, lead author and sociology professor at Duke University.