Tuberous sclerosis complex is a rare inherited condition that causes a combination of widespread tumours, epilepsy and neuropsychological problems including autism and learning difficulties. Everolimus is an effective drug for treating the tumours and epilepsy. This paper reports a clinical trial of twenty-four weeks of everolimus treatment compared with placebo (an identical appearing pill without everolimus in it) for neuropsychological problems in adults with tuberous sclerosis complex. Surprisingly, these problems improved in both those receiving everolimus and those receiving placebo. This could reflect participants becoming familiar with the tests and staff – a finding that may help design of future trials. (https://jmg.bmj.com/content/early/2026/08/06/jmg-2026-111529)