Behaviorally inhibited temperament is associated with severity of post-traumatic stress disorder symptoms and faster eyeblink conditioning in veterans

Figures & data

Table I.  Mean (SD) PCL-M total scores and scores for PTSD cluster B, C, and D symptoms in individuals with inhibited vs. uninhibited temperament based on AMBI and RMBI, and with vs. without combat history.

	Combat history (n = 126)		AMBI (n = 126)		RMBI (n = 123)
	Combat (n = 32)	Non-combat (n = 94)	Inhibited (n = 69)	Uninhibited (n = 57)	Inhibited (n = 62)	Uninhibited (n = 61)
PCL-M (total)	53.50* (17.91)	32.97 (16.00)	43.30* (19.56)	31.98 (15.70)	42.13 (18.99)	33.97 (17.18)
Cluster B symptoms	3.09* (2.02)	0.97 (1.68)	1.97* (2.13)	0.95 (1.67)	1.87 (2.17)	1.13 (1.72)
Cluster C symptoms	4.41* (2.24)	1.74 (2.32)	3.01* (2.65)	1.70 (2.30)	2.98 (2.71)	1.80 (2.26)
Cluster D symptoms	3.19* (1.93)	1.76 (1.77)	2.75* (1.81)	1.35 (1.75)	2.63 (1.90)	1.62 (1.76)

Note: Asterisks indicate significant differences (ANOVA with factors of combat history and AMBI/RMBI, with alpha corrected to 0.004 to protect against increased family-wise error) between inhibited/uninhibited and combat/non-combat veterans (F>4.00, p < 0.004). PCL-M, PTSD Checklist-Military version; AMBI/RMBI, Adult/Retrospective Measure of Behavioural Inhibition.

Table II.  Mean (SD) AMBI and RMBI total scores and subscale scores for the complete set of 126 veterans and for the subset of 87 veterans who produced useable eyeblink conditioning data.

	Total sample (n = 126)	Eyeblink sample (n = 87)
RMBI total score	12.7 (6.6)	12.6 (6.7)
Non-approach (NA)	4.5 (2.9)	4.5 (2.9)
Fearful inhibition (FI)	2.5 (2.3)	2.5 (2.3)
Risk avoidance (RA)	2.9 (1.4)	2.7 (1.4)
Shyness & sensitivity (SS)	2.8 (2.0)	2.9 (2.2)
AMBI total score	17.0 (6.1)	17.2 (6.4)
Non-approach (NA)	3.2 (1.5)	3.2 (1.6)
Fearful inhibition (FI)	7.2 (3.4)	7.3 (3.5)
Risk avoidance (RA)	3.5 (1.4)	3.5 (1.4)
Low sociability (LS)	3.2 (1.6)	3.3 (1.6)

Note: Note that RMBI scores were not available for three veterans in the larger sample, due to endorsement of “do not remember” responses for more than 50% of RMBI items; RMBI scores were available for all veterans in the eyeblink sample. AMBI/RMBI, Adult/Retrospective Measure of Behavioural Inhibition.

Figure 1.  (A) PCL-M scores are significantly higher in veterans with a history of exposure to combat (F(1,117) = 36.41, p < 0.001. (B) Veterans classed as inhibited (based on either AMBI or RMBI scores) score higher on PCL-M than veterans classed as uninhibited (Univariate ANOVAs, all F>8.00, all p < 0.010). Asterisks indicate significant differences (p < 0.050). PCL-M, PTSD Checklist-Military version; AMBI/RMBI, Adult/Retrospective Measure of Behavioural Inhibition.

Figure 2.  Eyeblink acquisition data. (A) Veterans in the delay group (CS and US overlap and co-terminate) showed more eyeblink-CRs than in the omission group (CR causes omission of US) (repeated-measures ANOVA, F(1,74) = 7.74, p = 0.007). (B) There was also a block × RMBI × PTSS interaction, such that, among individuals without current, severe PTSD symptoms (noPTSS), those with childhood BI (Inhib) made more CRs than those with an uninhibited temperament (Uninhib, F(1,56) = 4.55, p = 0.037). RMBI, Retrospective Measure of Behavioural Inhibition.

Figure 3.  Eyeblink extinction data. (A) Given their higher level of responding during acquisition, the delay group (CS and US overlap and co-terminate) showed significantly faster extinction than the omission group (CR causes omission of US) (repeated-measures ANOVA, F(1,62) = 6.29, p = 0.004). (B) Within the omission group, veterans with uninhibited childhood temperament showed fewer CRs than those with inhibited childhood temperament (independent-samples t-test, t(42) = 2.14, p = 0.039). (C) Among non-combat veterans, those with inhibited current temperament showed more CRs during the first extinction block than those with uninhibited current temperament (independent-samples t-test, t(22) = 2.11, p = 0.047). N is shown at the base of each bar in (B) and (C). Asterisks indicate significant difference (p < 0.050).

Figure 4.  Eyeblink extinction data. (A) There was no difference in acquisition or extinction as a function of PTSS in the delay group (CS and US overlap and co-terminate) (all p>0.050). (B) In the omission group (CR causes omission of US), veterans with PTSS showed more eyeblink-CRs than those without PTSS during extinction blocks 1 and 2 (independent-samples t-tests, all t>2.00, all p < 0.050) but not during blocks 3–5 (all t < 1.5, all p>0.100). PTSS, severe, current PTSD symptoms. Asterisks indicate significant differences (p < 0.050).