| Symptoms | Number |
| Duration (>10 days) |
| Severity |
| Signs | Prolonged loss of consciousness (>1 min), amnesia |
| Sequelae | Concussive convulsions |
| Temporal | Frequency—repeated concussions over time |
| Timing—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 concussion |
| Age | Child and adolescent (<18 years old) |
| Co- and pre-morbidities | Migraine, depression or other mental health disorders, attention deficit hyperactivity disorder, learning disabilities, sleep disorders |
| Medication | Psychoactive drugs, anticoagulants |
| Behaviour | Dangerous style of play |
| Sport | High risk activity, contact and collision sport, high sporting level |