In his seminal article, Physiogenesis and Psychogenesis in the 'Post-Concussional Syndrome,' Lishman (1988) proposed that neurobiological factors account for the development of the post-concussion syndrome and psychological factors become primarily responsible for maintaining it in the chronic phase. Over the 20 years that followed, researchers have advanced our understanding of the etiology of the post-concussion syndrome. Our review of this evidence suggests that neurobiological and psychological factors play a causal role in post-concussion symptoms from the outset, and thus, Lishman's causal model should be updated. If we can clinically identify individuals on a trajectory of poor recovery in the acute post-injury stage, then we can direct secondary prevention towards modifiable risk factors.