Almost a quarter of young people are so dependent on their smartphones that they feel panicky or upset when the phone is unavailable, according to a global study.
By analysing literature published since 2011 when smartphones first became widespread, the range of studies showed that 10-30 per cent of children and young people used their smartphones in a dysfunctional way.
This means an average of 23 per cent of them were showing problematic smartphone usage (PSU), according to the researchers from King's College London in the UK.
PSU was defined as any behaviour linked to smartphones that has the features of an addiction, such as feeling panicky or upset when the phone is unavailable, they said.
The behaviour is also characterised by people finding it difficult to control the amount of time spent on the phone, and using the phone to the detriment of other enjoyable activities.
The study, published in the journal BMC Psychiatry, is the first to investigate the prevalence of PSU in children and young people at this scale, summarising findings from 41 studies that researched a total of 41,871 teenagers and young people.
The 41 studies included 30 from Asia, nine from Europe and two America. As many as 55 per cent of the participants were female, and young women in the 17 to 19-year-old age group were most likely to have PSU.
The researchers also investigated the links of this type of smartphone usage and mental health, and found a consistent association between PSU and poor measures of mental health in terms of depressed mood, anxiety, stress, poor sleep quality and educational attainment.
"In order to determine whether PSU should be classified as a behavioural addiction we need longitudinal data looking at PSU in relation to more objective health outcomes, as well as evidence that people with PSU struggle to moderate their use," said first author Samantha Sohn from the King's College London.
"Our review assesses the effects not just of heavy use, but of dysfunctional smartphone use, and by looking at an 'addicted' pattern of behaviour towards smartphones we have established correlations between this type of dysfunctional behaviour and poorer mental health outcomes," said Ben Carter, also from King's College London.
Over the past decade there has been an increase in smartphone use among children and young people and this has occurred at the same time as a rise in common mental disorders in the same age group, the researchers noted.
To help clarify the possible association between smartphone use and mental health in children and young people, the researchers investigated patterns of smartphone-related behaviour, rather than smartphone use per se.
"Smartphones are here to stay and there is a need to understand the prevalence of problematic smartphone usage. We don't know whether it is the smartphone itself that can be addictive or the apps that people use," said Nicola Kalk from the King's College London.