American Football, Rugby, MMA, UFC. All these adrenaline-filled sports bring in millions of viewers each year, and athletes put their bodies and brains on the line to excel in them.

But there’s increasing concern that head injuries are leading to serious mental health problems.

BBC Sport reporter Bobbie Jackson tells us about the research into this. He’s been speaking to the Concussion Legacy Foundation (CLF) to see what’s being done across different sports bodies.

We also hear from three athletes; Wayne Drew, Leeon Nyang, Terry Mngomezulu who tell us why they’re willing to take the risk and what drives their passion for the sport.

There’s also recognition about the links between concussion and a brain condition called CTE; chronic traumatic encephalopathy, that can only be diagnosed post-mortem. Michelle Roberts from the BBC’s Health team explains the symptoms.

This episode contains discussion about suicide and violence. Details of organisations offering information and support with these issues are available at bbc.co.uk/actionline.

Email: whatintheworld@bbc.co.uk WhatsApp: +44 0330 12 33 22 6 Presenter: Hannah Gelbart Producers: Benita Barden and Julia Ross-Roy Editors: Verity Wilde and Simon Peeks