Scrolling Twitter or refreshing Facebook definitely feels like it’s bad for you, as our attention spans rot and meaning is drained from our lives. Despite those strong feelings, we’re usually told the evidence isn’t yet there to prove social media damages our mental health. The evidence of surging mental ill health is strong, with 30% of 18- to 24-year-olds reporting a common mental disorder in 2018-19, up from 24% at the start of the millennium, so it’s hard not to worry that this debate echoes the mid-20th-century arguments that we hadn’t absolutely proved cigarettes cause cancer. Despite the strong correlation between smoking and dying, many doctors didn’t believe the link had been proved even by the 1960s. Reinforcing my prejudices is new research examining the staggered introduction of Facebook across US universities, launching in Harvard in 2004 and then spreading across the country. Using surveys of students, it shows the platform’s arrival saw them being more likely to report poor mental health with increases in depression and anxiety of 7% and 20% respectively. We’re talking about the negative impact of Facebook being around 22% of that of losing a job – this is big. The authors argue the impact is from increasing social comparisons. Seeing everyone else having a great time isn’t good if you’re not. The research shows that Facebook’s arrival increased students’ perceptions of how much other students were drinking – a fairly good proxy for how much fun you think others are having at that age – but had no effect on actual drinking levels. The youth of today might not smoke but it’s hard to believe newer forms of addiction are completely harmless.