In my view Jean Twenge is right because there have been lots of experiments and the result is sadness. More specifically I believe that
smartphones make kids sad because IGen asked teens to participate in a social experiment and had some teens use their smartphones and some not to. For example, In the end of the social experiment the teens that didn't use their smartphones seemed happier then the teens that used their smartphones. Although Twenge might object that correlation doesn't prove causation. I maintain that It causes depression, anxiety and loneliness. For example say someone post a picture on instagram of themselves and they don't get a lot of likes they can get sad and think no one likes them. Therefore, I conclude that kids and teens are getting sad (depression, anxiety, and loneliness) because people can be mean on texting apps and social media