Table 2.

Demographic and clinical characteristics of PTSD and non-PTSD twin pairs.

	PTSD		Non-PTSD		Two-factor ANOVA
	Exposed (n = 17)	Unexposed (n = 17)	Exposed (n = 23)	Unexposed (n = 23)	Diagnosis		Exposure		Interaction
					F1,76	P	F1,76	P	F1,76	P
Age (years)	53.1 (3.3)	53.1 (3.3)	51.8 (2.3)	51.8 (2.3)	3.8	0.05	-	-	-	-
Education (years)	13.5 (2.6)	14.3 (2.8)	14.7 (2.4)	14.7 (2.6)	1.8	0.18	0.45	0.51	0.55	0.46
MAST*	20.2 (17.6)	6.8 (10.4)	2.4 (4.5)	2.5 (4.0)	22.8	<0.001	8.4	0.005	8.5	0.005
Non-combat trauma† (number of events)	7.9 (2.6)	5.3 (3.8)	5.1 (4.0)	4.2 (3.0)	6.1	0.02	4.9	.03	1.3	0.26
Combat severity	7.9 (1.9)	-	3.5 (2.6)	-	67.4	<0.001	-	-	-	-
CAPS‡	72.2 (16.6)	-	6.2 (7.3)	-	577.7	<0.001	-	-	-	-

Data given as mean (s.d.).

^*Michigan Alcoholism Screening Test. Data is missing for one PTSD pair and two non-PTSD pairs. Follow-up t-tests: ExP+ versus ExP−, t₃₇ = 4.63, P < 0.0001; UxP+ versus UxP−, t₃₅ = 1.70, P = 0.09; ExP+ versus UxP+, t₁₅ = 2.92, P = 0.01; ExP− versus UxP−, t₂₀ = 0.14, P = 0.89.

^†Lifetime number of non-combat potentially traumatic events. Data is missing for one PTSD pair and two non-PTSD pairs. Follow-up t-tests: ExP+ versus ExP−, t₃₇ = 2.51, P = 0.02; UxP+ versus UxP−, t₃₆ = 0.96, P = 0.34; ExP+ versus UxP+, t₁₅ = 2.51, P = 0.02; ExP− versus UxP, t₂₀ = 0.64, P = 0.53.

^‡Clinician-Administered PTSD Scale (total symptom score)