84%, a variation possibly caused by different populations or study methodologies. The estimated incidence of PPCS (persistent postconcussive syndrome) is around 10% of mTBI cases. Since PCS by definition only exists in people who have had a head injury, demographics and risk factors are similar to those for head injury; for example, young adults are at higher risk than others for receiving head injury, and, consequently, of developing PCS. The existence of PCS in children is controversial. It is possible that children's brains have enough plasticity that they are not affected by long-term consequences of concussion (though such consequences are known to result from moderate and severe head trauma). On the other hand, children's brains may be more vulnerable to the injury, since they are still developing and have fewer skills that can compensate for deficits. Clinical research has found higher rates of post-concussion symptoms in children with TBI than in those with injuries to other parts of the body, and that the symptoms are more common in anxious children. Symptoms in children are similar to those in adults, but children exhibit fewer of them. Evidence from clinical studies found that high school-aged athletes had slower recoveries from concussion as measured by neuropsychological tests than college-aged ones and adults. PCS is rare in young children. Risk factors A wide range of factors have been identified as being predictive of PCS, including low socioeconomic status, previous mTBI, a serious associated injury, headaches, an ongoing court case, age and female sex. Being older than 40 and being female have also been identified as being predictive of a diagnosis of PCS, and women tend to report more severe symptoms. In addition, the development of PCS can be predicted by having a history of alcohol use disorder, low cognitive abilities before the injury, a personality disorder, or a medical illness not related to the injury. PCS is also more prevalent in people with a history of psychiatric conditions such as clinical depression or anxiety before the injury. Mild brain injury-related factors that increase the risk for persisting post-concussion symptoms include an injury associated with acute headache, dizziness, or nausea; an acute Glasgow Coma Score of 13 or 14; and having another head injury before recovering from the first. The risk for developing PCS also appears to be increased in people who have traumatic memories of the injury or expect to be disabled by the