Table 2.  .

Factors That May Modify the Risk of Concussion and Duration of Recovery⁷

Risk	Modifiers
Symptoms	Number
	Duration (>10 d)
	Severity
Signs	Prolonged loss of consciousness (>1 min), amnesia
Sequelae	Concussive convulsions
Temporal	Frequency: repeated concussions over time
	Time: injuries close together in time
	Recency: recent concussion or traumatic brain injury
Threshold	Repeated concussions occurring with progressively less impact, force, or slower recovery after each successive event
Age	Child or adolescent (<18 y)
Comorbidities and premorbidities	Migraine, depressions, or other mental health disorders; attention-deficit hyperactivity disorder; learning disabilities; sleep disorders
Medication	Psychoactive drugs, anticoagulants
Behavior	Dangerous style of play
Sport	High-risk activity, contact or collision sport, high sporting level