Measuring workplace trauma response in Australian paramedics: an investigation into the psychometric properties of the Impact of Event Scale

Figures & data

Table 1 Populations yielding a two-factor solution from IES administration

Population	n	Method	Variance explained (%)	Reference
Male combat veterans	382	PCA with Varimax rotation	57.0	Schwarzwald et al^Citation54
Adult survivors of a cruise ship disaster	73	PCA (rotation undefined)	56.0	Joseph et al^Citation55
Adolescent survivors of a cruise ship disaster	334	PCA with Varimax rotation	61.1	Yule et al^Citation56
Female bank staff who were victims of armed raids	228	PCA with Varimax rotation	55.6	Hodgkinson and Joseph^Citation57
War veterans	281	PCA with Varimax rotation	47.7	Robbins and Hunt^Citation58
Italian road accident survivors	74	PCA with Quartimax rotation	44.3	Pietrantonio et al^Citation29
Non-clinical sample of American college students	304	Maximum likelihood factor analyses with Varimax rotation	55.3	Thatcher and Krikorian^Citation30

Abbreviations: PCA, principal component analysis; IES, Impact of Event Scale.

Table 2 Sample characteristics

Characteristic	n	M	SD
Age (years)		40.9	9.0
Hours worked per week		45.2	10.7
Years in occupation		14.7	9.2
Hours in direct client contact		25.8	12.9
Practice location
Urban	105
Rural or remote	122
Undefined	3
Sex
Female	55
Male	172
Undefined	3

Abbreviations: M, means; SD, standard deviation.

Table 3 Initial rotated factor matrix for maximum likelihood factor analysis with Varimax rotation of IES items and communalities (N=230)

Item	h^2	F1	F2
I4: Pictures about it popped into my mind	0.70	0.76	0.37
I2: Other things kept making me think about it	0.63	0.72	0.33
I7: I had dreams about it	0.54	0.67	0.32
I5: Any reminder brought back feelings about it	0.62	0.64	0.46
I1: I had waves of strong feelings about it	0.56	0.61	0.43
I6: I had trouble falling asleep or staying asleep because of pictures or thoughts about it that came into my mind	0.58	0.61	0.46
A1: I was aware that I still had a lot of feelings about it, but I did not deal with them	0.60	0.58	0.52
A5: My feelings about it were kind of numb	0.42	0.56	0.32
A6: I felt as if it had not happened or was not real	0.29	0.51	0.16
A3: I tried to remove it from memory	0.72	0.29	0.80
A2: I avoided letting myself get upset when I thought about it or was reminded of it	0.56	0.24	0.71
A8: I tried not to think about it	0.66	0.44	0.68
A7: I stayed away from reminders of it	0.58	0.49	0.58
I3: I thought about it when I did not mean to	0.52	0.45	0.56
A4: I tried not to talk about it	0.47	0.44	0.52

Notes: Factor loadings >0.40 are in boldface. h², Communalities; F₁, Intrusion; F₂, Avoidance. Items in table are presented in order of original presentation in Horowitz et al.¹

Abbreviation: IES, Impact of Event Scale.

Table 4 Final rotated factor matrix for maximum likelihood factor analysis with Varimax rotation of IES items, communalities and congruence coefficients for an ideal target matrix (N=230)

Item	h^2	F1	F2	CC
I4: Pictures about it popped into my mind	0.76	0.80	0.35	0.92
I2: Other things kept making me think about it	0.67	0.75	0.33	0.92
I7: I had dreams about it	0.55	0.66	0.34	0.89
I6: I had trouble falling asleep or staying asleep because of pictures or thoughts about it that came into my mind	0.59	0.63	0.43	0.83
I5: Any reminder brought back feelings about it	0.61	0.58	0.52	0.75
I1: I had waves of strong feelings about it	0.53	0.56	0.46	0.78
A8: I tried not to think about it	0.71	0.40	0.75	0.88
A3: I tried to remove it from memory	0.65	0.32	0.75	0.92
A7: I stayed away from reminders of it	0.61	0.42	0.66	0.84
A2: I avoided letting myself get upset when I thought about it or was reminded of it	0.48	0.28	0.64	0.91
A1: I was aware that I still had a lot of feelings about it, but I did not deal with them	0.61	0.51	0.59	0.75
A4: I tried not to talk about it	0.48	0.39	0.58	0.82
Congruence coefficient (CC)		0.85	0.86	0.85

Notes: Factor loadings >0.40 are in boldface. h², Communalities; F₁, Intrusion; F₂, Avoidance.

Abbreviation: IES, Impact of Event Scale.

Table 5 Subscale alpha, means, standard deviations, Kurtosis, and Skewness coefficients

Subscale	Item	α	M	SD	S	K
Avoidance		0.89
	A1: I was aware that I still had a lot of feelings about it, but I did not deal with them		0.88	1.45	1.67	1.70
	A2: I avoided letting myself get upset when I thought about it or was reminded of it		1.57	1.88	0.78	−0.92
	A3: I tried to remove it from memory		1.33	1.82	1.00	−0.51
	A4: I tried not to talk about it		0.94	1.60	1.65	1.35
	A5: My feelings about it were kind of numb		0.68	1.35	2.10	3.36
	A6: I felt as if it had not happened or was not real		0.45	1.09	2.90	8.10
	A7: I stayed away from reminders of it		0.76	1.44	1.96	2.68
	A8: I tried not to think about it		1.29	1.75	1.09	−0.25
Intrusion		0.90
	I1: I had waves of strong feelings about it		1.36	1.65	0.94	−0.39
	I2: Other things kept making me think about it		1.05	1.44	1.17	0.20
	I3: I thought about it when I did not mean to		1.31	1.61	0.97	−0.31
	I4: Pictures about it popped into my mind		1.08	1.44	1.22	0.44
	I5: Any reminder brought back feelings about it		1.07	1.58	1.34	0.53
	I6: I had trouble falling asleep or staying asleep because of pictures or thoughts about it that came into my mind		1.09	1.53	1.17	0.11
	I7: I had dreams about it		0.54	1.07	2.30	4.98

Abbreviations: M, mean; SD, standard deviations; S, Skewness; K, Kurtosis.

SchwarzwaldJSolomonZWeisenbergMMikulincerMValidation of the impact of event scale for psychological sequelae of combatJ Consult Clin Psychol19872552512563571682

 PubMed Web of Science ®Google Scholar

JosephSYuleWWilliamsRHodgkinsonPThe Herald of Free Enterprise disaster: measuring post-traumatic symptoms 30 months onBr J Clin Psychol199332Pt 33273318251963

 PubMed Web of Science ®Google Scholar

YuleWTen BruggencateSJosephSPrincipal component analysis of the Impact of Event Scale in children who survived a shipping disasterPers Individ Dif199416685691

 Web of Science ®Google Scholar

HodgkinsonPJosephSFactor analysis of the Impact of Events Scale with female bank staff following an armed raidPers Individ Dif199519773775

 Web of Science ®Google Scholar

RobbinsIHuntNValidation of the IES as a measure of the long-term impact of war traumaBr J Health Psychol19961Part 18789

 Web of Science ®Google Scholar

PietrantonioFGennaroLDDi PaoloMCSolanoLThe impact of event scale: validation of an Italian versionJ Psychosom Res200355438939314507552

 PubMed Web of Science ®Google Scholar

ThatcherDLKrikorianRExploratory factor analysis of two measures of posttraumatic stress disorder (PTSD) symptoms in a non-clinical sample of college studentsJ Anxiety Disord200519890491416243638

 PubMed Web of Science ®Google Scholar

HorowitzMJWilnerNAlvarezWImpact of event scale: a measure of subjective stressPsychosom Med1979413209218472086

 PubMed Web of Science ®Google Scholar