The brain starts a slow downward slide at about 25. By 40, this decline speeds up.

Concussions before puberty can have better chance of recovery. Puberty puts a load on the brain that lasts until about 20. Concussions during puberty can cause a myriad of symptoms.

The factors that make the most difference is prior history of concussions and sub-concussive impacts. Many who suffer a concussion after 25 or even later have a history of sub-concussive impacts or concussions that make their PCS worse.

A history of getting seriously drunk can put the brain at greater risk, especially if the alcohol abuse is during the teens.