Table.

Group mean demographic, self-report, and dependent measures for the combat-exposed and combat-unexposed veterans

	Full Sample				Non-medicated, non-Smoking Subsample
	ExP+ (n=37)	ExP− (n=47)	UxP+ (n=37)	UxP− (n=48)	ExP+ (n=8)	ExP− (n=21)	UxP+ (n=13)	UxP− (n=21)
Measure	M (SD)	M (SD)	M (SD)	M (SD)	M (SD)	M(SD)	M (SD)	M (SD)
Age*	49.6 (2.7)	49.0 (2.2)	49.9 (4.0)	49.0 (2.2)	48.5 (2.5)	49.7 (2.2)	51.5 (5.5)	49.3 (2.2)
Combat Severity	7.4 (2.6)	3.8 (2.5)	__	__	7.3 (3.3)	3.3 (2.2)	__	__
Months in Vietnam	12.3 (5.9)	11.9 (3.9)	__	__	12.3 (1.8)	11.1 (2.6)	__	__
Mississippi Scale†	121.8 (23.9)	72.1 (17.8)	__	__	113.5 (26.3)	67.0 (17.3)	__	__
CAPS Total	70.1 (17.7)	7.6 (8.2)	__	__	64.1 (18.8)	6.3 (8.0)	__	__
Target P3b Amp	11.0 (4.4)	11.7 (3.8)	11.5 (6.2)	10.9 (4.5)	9.4 (4.5)	13.2 (3.9)	12.9 (5.1)	11.2 (4.1)
Target N2 Latency‡	232.8 (19.0)	225.0 (16.3)	228.6 (17.0)	225.4 (15.8)	__	__	__	__
Mean Reaction Time§	437.9 (110.8)	432.0 (97.9)	419.9 (81.7)	421.7 (86.4)	459.5 (126.5)	419.5 (75.9)	381.3 (49.7)	429.1 (102.7)

Abbreviations: ExP+=combat exposed twin with PTSD; UxP+=combat unexposed co-twin of twin with PTSD; ExP−=combat-exposed twin without PTSD; UxP−=combat-unexposed co-twin of twin without PTSD; PTSD=posttraumatic stress disorder; CAPS Total=Clinician-Administered PTSD total scale score.

^*Age as of October 1, 1997.

^†Mississippi Scale for Combat–Related PTSD

^‡The following number of participants had unscorable N2 components: ExP+=11; UxP+=14; ExP−=11; UxP−=12.

^§To the target stimuli, in ms.