How many young people have been found to have mental health issues related to mobile phone?

Question: How many young people have been found to have mental health issues related to mobile phone?
- Keywords:
  health,
  screen time,
  technology
Asked by anon-228656 to Alex, Jolel on 11 Nov 2019. This question was also asked by anon-228764.
- Alex Spiers answered on 11 Nov 2019:
  
  The real answer is we don’t know yet. NOt enough research has been done on this. Scientists have hypotheses, and predictions, but smartphones are such new technology, that is unclear what the LONG-TERM effects are.

Question: How many young people have been found to have mental health issues related to mobile phone?