How social media makes us feel so bad about ourselves. Social media is liked to an array of mental health problems, including depression, anxiety and addiction. But what is behind these effects? New computational neuroscience has shed light on how the architecture of these platforms poses a problematic 'hyperstimulant' delivery system that rewards addictive behaviour. Mark Miller, a philosopher of cognition, and Ben White, a PhD student of neuroscience and digital technology, explore how this emerging discovery lends weight to the voices calling for a change in how social media is designed, operated and regulated.