Table 3.

Comparing the 2014 preliminary research diagnostic criteria to the 2021 consensus criteria for traumatic encephalopathy syndrome.

	2021 Consensus Criteria (36)	2014 Preliminary Research Criteria (35)
Exposure Criteria	Substantial exposure to repetitive head impacts (e.g., 5 or more years of football, with at least 2 years at the high school level). Other types of exposures are included but are not clearly defined (e.g., military occupational exposures to low-level blast). Comment: Mild, moderate, and severe TBIs are not considered to be part of the exposure criteria. The exposure criterion does not consider concussions and it is much less/lower than the criterion from 2014.	History of multiple impacts to the head (or to the body resulting in impulsive force transmitted to the head) from a variety of sources, including: (i) a minimum of four or more mild TBIs; (ii) a minimum of two or more moderate–severe TBIs, and/or (iii) subconcussive trauma from playing sports, military service, or domestic violence. For sports, a minimum of 6 years was required, including at least 2 years at the college level or higher.
Core Diagnostic Features	‘Diagnosis of TES requires (1) substantial exposure to repetitive head impacts (RHIs) from contact sports, military service, or other causes (2); core clinical features of cognitive impairment (in episodic memory and/or executive functioning), neurobehavioral dysregulation, or both (3); a progressive course; and (4) that the clinical features are not fully accounted for by any other neurologic, psychiatric, or medical conditions’ (pg. 848) (36). Comment: The authors stated that intermittent explosive disorder does not meet the criterion for neurobehavioral dysregulation.	For diagnosis, one of three core features must be present: (i) difficulties with cognition (subjective and objectively measured); (ii) being emotionally explosive, physically violent, or verbally violent; and/or (iii) feeling overly sad, depressed, and/or hopeless. Comment: The authors stated that a formal diagnosis of intermittent explosive disorder meets the second core criterion but is not necessary for diagnosis. They also stated that diagnoses of major depressive disorder or persistent depressive disorder meet the third core criterion but are not necessary for diagnosis (35). The 2021 criteria are substantially different and no longer include psychiatric disorders as core or supportive diagnostic features.
Supportive Features (2021)/Supportive Diagnostic Criteria (2014)	Supportive features are not required for diagnosis. The three supportive features are (i) delayed onset of symptoms, (ii) motor signs [e.g., a diverse range of Parkinsonian signs (e.g., bradykinesia, tremor, gait disorder), upper motor neuron signs (e.g., spasticity or hyperreflexia), lower motor neuron signs (e.g., fasciculations and muscle atrophy), and/or amyotrophic lateral sclerosis], and (iii) psychiatric features (e.g., a diverse range of psychiatric problems, occurring singly or in combination, that are persistent or progressive, including anxiety disorders, depressive disorders, apathy, and paranoia) (36).	A minimum of two of the following nine supportive criteria must be present: (i) impulsivity (e.g., excessive gambling, substance abuse, or excessive shopping); (ii) anxious mood, agitation, excessive fears, or obsessive or compulsive behavior (or both); (iii) apathy (e.g., loss of interest in usual activities, loss of motivation and emotions); (iv) paranoia (e.g., delusional beliefs or unwanted jealousy); (v) suicidality (history of suicidal thoughts or attempts); (vi) headache (at least once per month for six months), (vii) motor signs (e.g., dysarthria, bradykinesia, tremor, gait disturbance, and/or other features of Parkinsonism), (viii) documented decline in function or symptoms for at least one year; and (ix) delayed onset (onset of clinical features at least two years after the exposure to repetitive head impacts) (35).
Must be a Progressive Clinical Condition	Yes. This is a required diagnostic feature.	No. Being progressive is one of nine possible supportive diagnostic criteria, for at least one year, and is “based upon repeated formal testing, clinician examination, or other formal measurement” (page 11)
Can be Diagnosed Based Entirely on Mental Health Problems	No. Comment: This is a major change from the 2014 criteria and how TES/CTE has been described in the literature between 2009 and 2021.	Yes. Comment: For example, former college football, rugby, or hockey players who develop depression, anxiety, and suicidality any time during middle or late adulthood could (would) meet criteria for TES.