Table 1 Demographic and clinical characteristics in IC, mTBI and smcTBI groups.

	IC (n = 45)	mTBI (n = 107)	smcTBI (n = 66)	Significance
Sex (male)	41 (91.0%)	100 (93.0%)	63 (95.0%)	X² = 0.85, df = 2, p = 0.655¹
Age (years)
Median [IQR]	35 [27–43]	32 [26–42]	30 [24–40]	p = 0.599²
Race
White	32 (71.0%)	80 (75.0%)	54 (82.0%)	X² = 2.03, df = 4, p = 0.730¹
African American	6 (13.0%)	13 (12.0%)	5 (7.6%)
Other	7 (16.0%)	14 (13.0%)	7 (11.0%)
Education (years)
Median [IQR]	14.00 [13.00–16.00]	14.00 [12.00–16.00]	14.00 [12.00–16.00]	p = 0.510²
TSI (months)
Median [IQR]	9 [3–35]	35 [6–92]	10 [5–60]	p = 0.012*²
Number of TBIs
Median [IQR]	N/A	1 [1, 2]	1.00 [1–1]	p = 0.050³
TBI severity^a
Uncomplicated mTBI	0 (0%)	107 (100%)	0 (0%)	N/A
Complicated mTBI	0 (0.0%)	0 (0.0%)	31 (47.0%)
Moderate TBI	0 (0.0%)	0 (0.0%)	19 (28.8%)
Severe TBI	0 (0.0%)	0 (0.0%)	16 (24.2%)
PCD Dx (yes)	12 (30.8%)	30 (32.6%)	19 (32.8%)	X² = 0.07, df = 2, p = 0.965¹
NSI total
Median [IQR]	19 [12–26]	19.0 [8–31]	15.0 [6–35]	p = 0.857²
PTSD Dx (Yes)	5 (12.8%)	16 (17.4%)	12 (20.7%)	X² = 1.09, df = 2, p = 0.581¹
PCL-C total
Median [IQR]	26.0 [21–36]	27.0 [21–37]	24.0 [19–38]	p = 0.509²
Symptom validity^b
Yes	39 (89.0%)	92 (86.0%)	58 (89.0%)	X² = 0.46, df = 2, p = 0.796¹
No	5 (11.1%)	15 (14.0%)	7 (11%)
Missing	1 (2.2%)	0 (0.0%)	1 (1.5%)

Statistical tests: ¹Chi-square test (χ2) test, ²Kruskal–Wallis test, ³Mann–Whitney U test. *compared between mTBI and smcTBI groups.
IC, injured controls; mTBI, uncomplicated mild TBI; smcTBI, complicated mTBI, moderate TBI, and severe TBI combined; TBI, traumatic brain injury; TSI, time since injury; PCD Dx, classified as meeting DSM-IV Category C symptom criteria for postconcussional disorder; PTSD Dx, classified as meeting DSM-IV-TR symptom criteria for post-traumatic stress disorder; PCL-C, PTSD Checklist-civilian Version; NSI, Neurobehavioral Symptom Inventory.
^aTBI severity classification: [1] uncomplicated mild TBI: (i) GCS = 13–15, PTA < 24 h, LOC < 30 min, and/or AOC present, and (ii) no trauma-related intracranial abnormality on CT or MRI; [2] complicated mild TBI: (i) GCS = 13–15, PTA < 24 h, LOC < 30 min, and/or AOC present, and (ii) trauma-related intracranial abnormality on CT or MRI; [3] moderate TBI: LOC 30 min–24 h, PTA 1–7 days, and ICA present or absent; and [4] severe TBI: LOC > 24 h, PTA > 7 days, and ICA present or absent.
^bParticipants were not included in the behavioral analysis using NSI and PCLC if they scored below the recommended cutoffs on the validity scales of the MMPI-2-RF.

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