Table 1.

Group means (sd) of combat-exposed Vietnam veterans with and without PTSD and their combat-unexposed, identical co-twins

PTSD Pairs*			Non-PTSD Pairs†			Mixed Model ANOVA
	Exposed (n=14)	Unexposed (high risk) (n=14)	Exposed (n=19)	Unexposed (low risk) (n=19)	Diagnosis F(1,31)	p	Exposure F(1,32)	p	Interaction F(1,31)	p
Age (years)‡	57.8 (2.8)		57.1 (2.2)		0.6	ns
Education (years)	14.1 (2.4)	13.5 (2.3)	14.0 (1.9)	13.4 (1.8)	0.0a	ns	1.6b	ns	0.0a	ns
MAST#	9.3 (5.7)	8.4 (5.5)	6.3 (2.3)	5.6 (2.9)	4.7c	0.04	1.1d	ns	0.00c	ns
Combat everity¶	8.8 (2.0)		4.2 (3.0)		24.2	<.0001
CAPS§-Current	66.0 (25.8)		6.6 (9.3)		86.4	.0001
CAPS§- Lifetime	90.9 (25.5)		10.6 (12.0)		145.2	.0001
BDI¥	12.2 (11.7)	2.9 (3.8)	3.1 (3.6)	4.4 (5.5)	3.7e	ns	7.3f	.02	12.8e	.002
CTQ❷	58.6 (8.7)	55.2 (17.8)	61.3 (8.3)	61.2 (2.9)	2.6	ns	0.5	ns	0.5	ns
PANAS£-Positive Affect	21.7 (7.9)	22.4 (5.4)	23.9 (8.9)	21.8 (5.7)	0.2b	ns	0.2g	ns	0.8b	ns
PANAS£-Negative Affect	17.0 (8.7)	11.5 (2.3)	11.8 (3.4)	10.9 (1.2)	6.5b	.02	7.4g	.01	3.7b	.07

^*As determined by the presence of current, combat-related PTSD in the combat-exposed twin

^†As determined by the absence of current or past, combat-related PTSD in the combat-exposed twin

^‡As of January 1, 2005

^#Michigan Alcoholism Screening Test (range 0–25)

^¶18-item measure (range 0–18)

^§Clinician-Administered PTSD Scale (range 0–136)

^¥Beck Depression Inventory (range 0–63)

^❷Childhood Trauma Questionnaire

^£Positive and Negative Affect Schedule

^adf=1,29;

^bdf=1,30;

^cdf=1,28;

^ddf=1,29;

^edf=1,27;

^fdf=1,28;

^gdf=1,31