A I do think that the concerns Twenge raises are valid. I have her same concerns. I constantly hear from parents who are struggling with their own version of these problems: Teens who are too busy online to come out of their room. Young adults who may be remarkably adept in front of a computer, but lack some of the practical life skills they’ll need when they stop away from the keyboard.
B Twenge reviews only those studies that support her idea and ignores studies that suggest that screen use is not associated with outcomes like depression and loneliness or that suggest that active social media use is actually associated with positive outcomes like resilience.
C The studies Twenge reviews largely ignore social contexts and how people differ, instead reporting only average effects and correlations. Twenge should have taken into account these sorts of factors to maybe conclude that "moderate use of digital technology is not intrinsically harmful and may be advantageous in a connected world” just as Andrew K. Przybylski and Netta Weinstein did.
D There is no plausible reason to think that smartphones and social media may have only negative effects on kids. Kristelle Lavallee, Content Strategist at the Center on Media and Child Health out of Boston Children's Hospital, told me in an interview about many of the beneficial effects of social media on adolescent development.