There is a lot of concern, yes, and no shortage of correlational type anecdata, sure.

Caution is well advised ... but hard drug equivalent causal effect? Not so much.

Scientists pour cold water on claims phones are rewiring kids' brains

  Appearing before the Science, Innovation and Technology Committee this week, three researchers spent much of the session explaining that concern and evidence are not quite the same thing. 

  Asked what evidence exists on the impact of digital devices on infants and young children, Professor Denis Mareschal, director of the Centre for Brain and Cognitive Development at Birkbeck, replied: "There is very little, if any, causal research in the early years. Almost everything is correlational."

  MPs kept coming back to the question – and the experts kept coming back to the same answer.

  When questioned about social media's impact on adolescents, Professor Sarah-Jayne Blakemore of the University of Cambridge was equally cautious. "What evidence do we have of the impact of digital devices or social media on the adolescent brain?" she asked. "Almost nothing. There are a few small studies, but they haven't been replicated, and they're purely correlational."