Smartphones and tablets are causing mental health problems in children as young as two, according to new research.
Just an hour’s screen time a day can make them prone to heightened levels of anxiety or depression.
They may begin to have less curiosity, self control and emotional stability – and a greater inability to finish tasks.
Adolescents are most at risk although the phenomenon is also being seen in under tens – including tots, warn psychologists.
Establishing possible causes and outcomes is especially important to prevent low mental well being in children and teenagers, say the US team.
Children’s brains are more sensitive to the effects of electronic devices as their brains are still developing.
Professor Jean Twenge, of San Diego State University, and Professor Keith Campbell, of the University of Georgia, said: “Half of mental health problems develop by adolescence.
“Thus, there is an acute need to identify factors linked to mental health issues that are amenable to intervention in this population, as most antecedents are difficult or impossible to influence.
“Compared to these more intractable antecedents of mental health, how children and adolescents spend their leisure time is more amenable to change.”
This means parents, and teachers, cutting the amount of time they are online or watching television when studying, socialising, eating and even playing sport.
Last year University of Oxford researchers found ‘zombie’ British children spend almost five hours a day watching screens due to the rise of electronics.
Prof Twenge said her study, one of the biggest of its kind, backs the American Academy of Pediatrics’ established screen time limits – one hour per day for those aged two to five, with a focus on high-quality programmes – are valid.
It also suggests a similar limit – perhaps two hours – should be applied to school aged children and adolescents, she added.
Profs Twenge and Cambell analysed data provided by the parents of more than 40,000 US children aged two to 17 for a nationwide health survey in 2016.
The questionnaire inquired about the youngsters existing medical care, any emotional, developmental or behavioural issues and behaviours – such as daily screen time.
Adolescents spending more than seven hours a day on screens were twice as likely to have been diagnosed with anxiety or depression as those who had an hour.
Overall, links between screen time and well being were larger among adolescents than young children.
Prof Twenge said: “At first, I was surprised the associations were larger for adolescents.
“However, teens spend more time on their phones and on social media, and we know from other research that these activities are more strongly linked to low well being than watching television and videos, which is most of younger children’s screen time.”
Even moderate use of four hours was also associated with lower psychological well-being than use of one hour a day.
Pre-schoolers, or under fives, who were high users were twice as likely to often lose their temper – and 46 per cent more prone to not be able to calm down when excited.
Among 14 to 17-year-olds, more than four in ten (42.2%) of those who spent more than seven hours a day on screens did not finish tasks.
This was compared with one in six (16.6%) who spent one hour daily – and about a quarter (27.7%) for those engaged for four hours.
About one in eleven (9%) of 11 to 13-year-olds who spent an hour with screens daily were not curious or interested in learning new things.
This was compared to one in seven (13.8%) compared who spent four hours and more than one in five (22.6%) who spent more than seven.
Writing in Preventative Medicine Reports, the professors said they were particularly interested in links between screen time and diagnoses of anxiety and depression in youngsters, which has not yet been studied in great detail.
They said: “Previous research on associations between screen time and psychological well being among children and adolescents has been conflicting, leading some researchers to question the limits on screen time suggested by physician organisations.”
The US National Institute of Health estimates children and adolescents commonly spend an average of five to seven hours on screens during leisure time. Evidence is growing this has adverse effects on overall health.
This year the World Health Organisation decided to include gaming disorder in the 11th revision of the International Classification of Diseases.
It is encouraging “increased attention of health professionals to the risks of development of this disorder” as gaming addiction may now be classified as a disease.
Prof Twenge is author of ‘iGen: Why Today’s Super-Connected Kids Are Growing Up Less Rebellious, More Tolerant, Less Happy – and Completely Unprepared for Adulthood.”
In December 2017 the Oxford team found UK kids average daily screen time has leapt in a generation from just under three hours to four hours and 45 minutes.
Experts warn ‘addicted’ children risk sleeplessness, obesity and falling victim to cyber-bullying, while losing valuable social skills through a lack of face-to-face contact.
By Ben Gelblum and Mark Waghorn