He left a note to send his brain for use in the ongoing study of the effect of concussions and head trauma on depression and suicide.

FORBES: The Future Will Reveal How Much Jovan Belcher's NFL Family Cares -- And is there Dysfunction in the NFL Family?

The report showed Seau had CTE, a brain disease linked head trauma, which can lead to depression.

FORBES: President Obama Questions Safety Of Playing Football

Quick wrote the book having himself worked with mental health patients, particularly those with head traumas, and having experienced deep depression himself.

BBC: Oscars: Silver Linings Playbook from page to screen