You can't convince them. But, you can inform them. Tell them that 15% of concussions cause prolonged problems and some cause lifelong struggles. Every brain responds differently. Every concussion is different.

As Bud said, This is the strangest party I have ever been to.

Wow, that Three Dog Night song ( Momma Told Me Not to Come, 1970 ) was a hit the same year I had my first bad prolonged problems from a concussion. Seizures, cognitive and memory problems. Dropped a full grade point as a high school sophomore. Just a bad header in soccer practice. Took me 2 years to recover to a functional level.