Smartphones are increasingly leaving teenagers lonely and depressed

Number of teenagers who spend daily time with friends dropped by 40% between 2005-15

Teenagers in the US on Monday are working less, having less sex and are far less happy than previous generations because of increased use of smartphones, says a social psychologist who has been researching generational differences for 25 years.

In an article for The Atlantic, adapted from her forthcoming book on the current generation -- the iGen, as she calls it, Jean Twenge says there is compelling evidence that the devices we have placed in young people's hands are having profound effects on their lives -- and making them seriously unhappy.

The statistics, as outlined by Twenge, are alarming, Fortune.com reported on Sunday.

While only 56 per cent of high school seniors dated in 2015, compared to 85 per cent for Gen Xers and Baby Boomers, the number of teenagers who spend daily time with friends dropped by 40 per cent between 2000 and 2015, it said.

The decline in dating tracks with a decline in sexual activity, Twenge said.

While this might have had a positive impact on the teenage birth rate which hit an all-time low in 2016, down 67 per cent since its modern peak in 1991, Twenge said that increased smartphone use is also linked to loneliness and depression among the post-millennial generation.

Today's teenagers are also working less than their predecessors and driving less, often depending on parents for the rides, according to the research.

So, if they are not meeting their friends, working less, and not often going on a date, what are they doing with all that time?

They are on their phone, in their room, alone and often distressed, Twenge said.