Concussion and its subsequent postconcussive symptoms were first described by p more than a century ago. Since then and through the early 2000s, concus characterized by a myriad of definitions and anecdotally based grading scales an to-play guidelines, miring this injury in controversy. During the past decade, the cation and management of concussive injury has undergone a dramatic “paradigm s Although many of the earlier issues that affect concussion practice and research co persist, including the adoption of consistent definitions and return-to-play guide field has evolved toward a more evidence-based approach. Postconcussion syndrome (PCS), the term most commonly used to refe collection of symptoms that occur after a concussion, remains an area of grea For many years, persons in the fields of neurology and psychiatry professed that co did not result in persistent somatic or behavioral effects [2]. Because treatment predicated on self-report of symptoms, many medical professionals continue t delayed recovery with psychological factors (eg, anxiety or depression) or financi (eg, medicolegal compensation) [3]. Fueling this argument is the fact that the sym PCS are not unique to the injury. Similar symptoms have been reported in uninjure control subjects, personal injury claimants, patients with depression, and patie chronic pain [4,5]. A syndrome is a collection of symptoms that, when taken together, charac underlying condition. Researchers have argued that the collection of symptoms ide PCS are so nonspecific that they do not fulfill requirements of this definition [6]. T recognized and cited definitions of PCS, which are from the Diagnostic and Statistica of Mental Diseases, 4th edition (DSM-IV) [7] and the International Classification of 10th revision (ICD-10) [http://www.ihs-classification.org/en/02_klassifikation/ 05.00.00_necktrauma.html, 8], differ in their language and diagnostic criteria (Ta a prospective study of patients with concussion 3 months after injury, Boake reported that when the DSM-IV criteria were used, the diagnosis rate of postcon disorder was 11%, compared with a diagnosis rate of 64% when the ICD-10 criteri were used. Neither the DSM-IV nor the ICD-10 criteria are specific in differentiating with PCS and/or postconcussional disorder from those with extracranial trauma DSM-IV criteria suggest that symptoms that persist for 3 months are required for the d whereas the ICD-10 criteria do not assert such a time frame. In summary, the inc criteria applied to PCS result in considerable inconsistencies in diagnosis and su treatment for patients with PCS. The debate regarding the diagnostic criteria of PCS revolves around the no nature of its symptoms; however, the underlying factors that may influence the inc PCS also have come under scrutiny. For example, researchers have argued that th incidence of PCS in countries such as the United States and the United Kingdom m medicolegal compensation systems in those countries, because the incidence of been lower in countries without such systems [10]. Mittenberg et al [11] also sug patients may have an “expectation” of symptoms after concussion and there attribute pre-existing symptoms to their concussion. Moreover, researchers have that, within military populations, comorbid post-traumatic stress disorder (PT depression confound the diagnostic criteria for PCS [12]. In the absence of unique biologic markers of concussion and PCS, the aforem issues will continue to invite controversy [13]. However, the emergence of valid and rel