Table 1.

Group mean (S.D.) demographic and psychometric data, whole brain and cerebellar vermis volumes, and results of mixed model, random effects analyses

		PTSDa		Non-PTSDa		PTSD diagnosisa		Combat exposure		Interaction
		(Ex: n=18)		(Ex: n=22)		tb	P	tb	P	tb	P
		(Ux: n=20)		(Ux: n=23)		Estimate	(95% CIs)c	Estimate	(95% CIs)c	Estimate	(95% CIs)c
		M	(S.D.)	M	(S.D.)
Age	Ex	52.5	(3.5)	51.7	(2.3)	0.7	0.48	-1.0	0.32	-1.2	0.23
	Ux	52.8	(3.2)	51.8	(2.3)	-	-	-	-	-	-
Educationd	Ex	13.6	(2.6)	14.6	(2.4)	-1.4	0.16	-0.2	0.86	-0.5	0.61
	Ux	13.5	(3.2)	14.7	(2.6)	-	-	-	-	-	-
CAPS scoree	Ex	74.4	(16.8)	5.9	(7.3)	24.6	<0.0001	-	-	-	-
	Uxf	72.6	(16.8)	6.2	(7.3)	-	-	-	-	-	-
Whole brain	Ex	1239	(119)	1261	(107)	-0.1	0.93	0.0	0.99	-2.2	0.04
volumeg	Ux	1268	(114)	1246	(112)	-	-	-	-	-	-
Anterior superior	Ex	1.39	(0.11)	1.40	(0.18)	-0.2	0.84	-1.7	0.10	-0.6	0.57
Vermis volumeg	Ux	1.43	(0.17)	1.43	(0.18)	-0.01	(-0.10, 0.08)	-0.03	(-0.07, 0.01)	-0.02	(-0.10, 0.06)
Posterior superior	Ex	0.87	(0.21)	0.89	(0.15)	-0.1	0.94	0.8	0.45	-0.4	0.67
Vermis volumeg	Ux	0.86	(0.16)	0.85	(0.18)	-0.00	(-0.09, 0.08)	0.02	(-0.03, 0.08)	-0.03	(-0.14, 0.09)
Inferior posterior	Ex	0.95	(0.14)	0.96	(0.11)	-0.7	0.52	-1.5	0.15	0.4	0.72
Vermis volumeg	Ux	0.96	(0.15)	1.00	(0.12)	-0.02	(-0.09, 0.04)	-0.03	(-0.07, 0.01)	0.02	(-0.07, 0.10)
Total	Ex	3.20	(0.32)	3.26	(0.35)	-0.3	0.74	-0.8	0.44	-0.3	0.79
Vermis volume g	Ux	3.25	(0.39)	3.28	(0.39)	-0.03	(-0.22, 0.16)	-0.04	(-0.15, 0.06)	-0.03	(-0.25, 0.19)

Ex = combat-exposed, Ux = combat-unexposed, PTSD = post-traumatic stress disorder, CAPS = Clinician-Administered PTSD Scale.

^aDiagnostic status of the combat-exposed twin.

^bMixed model t.

^cEstimate of the difference of the means with 95% confidence intervals.

^dGrades completed.

^eCombat-related PTSD symptoms.

^fCombat-exposed brother’s score.

^gVolumes in ml.