Around 370 BC Plato wrote the Phaedrus, a dialogue in which Socrates tells a story about the Egyptian god Theuth, who invented writing and offered it to King Thamus as a gift that would improve memory. The king disagreed. In Benjamin Jowett's 1871 translation he replies that "this discovery of yours will create forgetfulness in the learners' souls, because they will not use their memories; they will trust to the external written characters and not remember of themselves." Nearly every new medium since has met similar fears. Novels were said to corrupt young readers, radio dramas to frighten children and comic books to breed delinquency. Remembering this history helps us judge today's claims. It does not prove them wrong. Thamus had a point: tools that store memory do change how people use memory.

The case for alarm

Since about 2012, rates of depression, anxiety and self-harm among adolescents have risen in the United States, Britain and several other countries, especially among girls. The psychologist Jean Twenge, in her 2017 book iGen, and the social psychologist Jonathan Haidt, in The Anxious Generation (2024), argue that the timing is no coincidence. Around then, smartphones with front cameras and social media apps became nearly universal among teenagers. Haidt argues that a phone-based childhood displaced sleep, in-person play and independence, and broke attention into fragments. He proposes four norms: no smartphones before high school, no social media before 16, phone-free schools and far more independent play.

Supporters point to causal evidence. A 2022 study by Luca Braghieri, Ro'ee Levy and Alexey Makarin used the staggered arrival of Facebook at American colleges between 2004 and 2006 and found that Facebook's arrival worsened students' mental health, including reported depression. In another experiment, published in 2020 by Hunt Allcott and colleagues, people paid to deactivate Facebook for four weeks reported that their well-being rose modestly, and they spent the freed time on other things, including friends and family.

The case for caution

Other researchers think the alarm runs ahead of the evidence. In a 2019 study Amy Orben and Andrew Przybylski analyzed large datasets covering hundreds of thousands of adolescents and found that the link between digital technology use and well-being, though negative, was tiny, explaining at most about 0.4 percent of the variation. They compared it to the link with eating potatoes or wearing glasses. The psychologist Candice Odgers, reviewing Haidt's book in the journal Nature in 2024, argued that most studies are correlational, that the effects found are small, and that rising distress has other plausible causes, from academic pressure to economic worry.

Reading the debate well

Several principles help. First, correlation is not causation: unhappy teenagers may turn to phones more, rather than phones making them unhappy. Second, averages hide variation; a small average effect can mean little harm for most and serious harm for a vulnerable few. Third, what people do on screens matters more than total hours. Messaging a close friend and scrolling strangers' highlight reels are different activities. Fourth, natural experiments and randomized trials carry more weight than surveys, though they usually cover short periods. The honest summary today is that the evidence is genuinely contested, with researchers acting in good faith on both sides, and that waiting for perfect proof also has costs when children are involved.

Rewiring, used loosely

Claims that screens "rewire the brain" need care. All experience changes the brain; learning to juggle or to read rewires it too. The real question is whether a change is harmful, and answering that takes evidence about behavior, not brain images alone. In 2010 the writer Nicholas Carr argued in The Shallows that heavy internet use trains the mind for skimming at the cost of deep concentration. His book was influential and partly a personal report, and critics replied that people still read long novels and watch long series. Both points can hold at once: habits can shift without abilities disappearing.

Worked example: weighing a headline

A news site runs the headline "Screens Are Destroying Teen Brains." Ari, a parent, wants to know what to believe. First Ari checks the study behind it: a survey, so it shows a correlation, not a cause. Next Ari checks the size: heavy users are slightly more likely to report low mood, an effect comparable to several ordinary habits. Then Ari asks what was measured: total hours, not activities. Finally Ari looks for experiments and finds the Facebook rollout and deactivation studies, which suggest real effects for some people. Ari concludes that the headline overstates the case but that the concern is not foolish. The practical choice that follows is modest and reversible: keep phones out of bedrooms at night, which protects sleep whatever the final verdict on mental health turns out to be.