A large study of more than 75,000 people has found that moderate-to-severe traumatic brain injury (TBI) is linked to an increased risk of malignant brain tumours. Within 3 to 5 years of injury, 0.6% of patients with significant TBIs developed tumours, higher than those without TBI. Mild TBIs, such as concussions, did not show an elevated risk, the research found.