Influence of childhood adversity on health among male UK military personnel

Background Exposure to childhood adversity may explain why onlya minority of combatants exposed to trauma develop psychologicalproblems.

Aims To examine the association between self-reported childhood vulnerability and later health outcomes in a large randomlyselected male military cohort.

Method Data are derived from the first stage of a cohort study comparing Iraq veterans and non-deployed UK military personnel.We describe data collected by questionnaire from males in theregular UK armed forces (n=7937).

Results Pre-enlistment vulnerability is associated with being single, of lower rank, having low educational attainment andserving in the Army. Pre-enlistment vulnerability is associatedwith a variety of negative health outcomes. Two main factorsemerge as important predictors of ill health: a `family relationships'factor reflecting the home environment and an `externalisingbehaviour' factor reflecting behavioural disturbance.

Conclusions Pre-enlistment vulnerability is an important individual risk factor for ill health in military men. Awareness of suchfactors is important in understanding post-combat psychiatricdisorder.

INTRODUCTION

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INTRODUCTION

The majority of UK military personnel do not develop combat-related psychiatric injuries, despite enduring arduous operationalduties, including deployments to Iraq (Hotopf et al, 2006).Previous work has focused on military experiences (Yager et al, 1984; Elder & Clipp, 1988), but there is renewed interest inindividual factors which may predispose a minority of individualsto becoming unwell (Brewin et al, 2000; Ozer et al, 2003). Childhood vulnerability is understood to be an important modulatorof an individual's risk of later psychological problems, includingpost-traumatic stress disorder (PTSD; Engel et al, 1993; Zaidi & Foy, 1994).The aim of the current study is to examine the associationof such self-reported vulnerabilities with later health outcomes in a large randomly selected male military cohort.

METHOD

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METHOD

Sample
Full details of the study have been described previously (Hotopf et al, 2006). In brief, the study was the first phase of a cohort study ofUK military personnel in service at the time of the Iraq warin March 2003. In total, 4722 personnel who were deployed onthe initial 2003 invasion, code named TELIC 1, and 5550 personnelwho were not deployed on TELIC 1 (the `Era' cohort) completeda questionnaire on their childhood experiences, deployment experiencesand health outcomes (n=10 272). TELIC 1 was defined, for thepurposes of this study, as 18 January to 28 April 2003.

The 10 272 participants represented a response rate after threemailings and active follow-up of 61%. The main reason for non-responsewas inability to contact personnel. There was no evidence ofany response bias by health outcomes, and no difference inthe prevalence of medical downgrading (being unfit for duty)in non-responders (Tate et al, 2007).

As we have previously reported that there are important genderdifferences in the UK military (Rona et al, 2007) and theproportion of women in the military and in our sample is small,we have limited this analysis to men. In addition, because we have previously shown an interaction between reservist statusand deployment (Hotopf et al, 2006), which has been exploredin greater depth in another paper (Browne et al, 2007), welimit the present analyses to regular personnel. After exclusion,the sample size available for these analyses was 7937.

Questionnaire
Participants were sent a detailed 28-page questionnaire booklet.This included information that participation in the surveywas voluntary and that the research was being conducted independentlyof the UK Ministry of Defence. The questionnaire consistedof seven sections: (1) demographics; (2) service information;(3) experiences prior to deployment; (4) experiences on deployment;(5) experiences following deployment; (6) information on current health; and (7) background information, including past medicalhistory and adversity in childhood. The Era cohort were askedto complete sections 3–5 for their most recent deployment;thus it was possible to gain information on deployment experiencesfor individuals who had served on later Iraq deployments. Fulldetails of the questionnaire and measures have been describedpreviously (Hotopf et al, 2006) and are available in the onlinedata supplement to the current paper.

As part of section 7, participants were asked to give a trueor false response to a series of 16 questions (some adverseand some protective) which followed the stem statement `WhenI was growing up...'. Three categories were chosen: familyrelationships, parenting and adolescent behaviour. Three items were adapted from the Adverse Childhood Exposure study scale(ACE; Felitti et al, 1998), and the remaining items were singleitems based on the existing evidence from the general populationon childhood exposures for later adverse health outcomes foradolescents and young people (see online data supplement for further details).

Statistical analyses
From the 16 questions on childhood adversity, a four-point vulnerability count was created by scoring individuals reporting none orone adverse factor as 1, two or three factors as 2, four orfive factors as 3 and six or more factors as 4.

To measure exposure to trauma, a composite measure was derivedfrom the sum of a list of possible `trauma' exposures experiencedduring deployment. Participants' scores ranged from 0 to 16and were divided into three categories for the purposes ofanalysis (0–1, 2–3 and 4+).

All analyses were performed using STATA version 9.0 and statistical significance was defined as P<0.05. Associations between demographic and vulnerability factors were examined using chi-squaredtests and logistic regression analyses were performed to examinethe relationship between vulnerability factors and health outcomes (Clayton & Hills, 1993). Odds ratios, 95% confidence intervalsand two-sided P values are presented. All analyses were adjustedfor age, service, rank, educational status and marital status.

To identify the factor structure of the vulnerability variablesa tetrachoric principal-component factor analysis was undertaken.The Kaiser–Meyer–Olkin measure of sampling adequacywas 0.87 and therefore principal-component factor analysiswas deemed appropriate. The loading matrix was rotated to maximisethe correlations between each factor. Two factors were identifiedbased on the eigenvalues (>2.0).

RESULTS

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RESULTS

Frequency of pre-enlistment vulnerability
Pre-enlistment vulnerability was relatively common in this military population; 76% of those sampled reported at least two or morevulnerability markers while growing up: 37.5% had been in troublewith the police; 29.8% got shouted at a lot at home; 25.5%had been in fights at school; and 3.3% had spent time in localauthority care (Table 1).

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Table 1 Frequency of each vulnerability factor and vulnerability count

Demographic and service factors associated with high vulnerability
Higher vulnerability counts were associated with younger age,being in the Army, being a non-commissioned officer or otherrank, having low educational attainment and being divorced,separated or widowed (Table 2).

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Table 2 Vulnerability count according to demographic and service characteristics

Vulnerability count and associated health outcomes
Higher vulnerability counts were significantly associated withall health outcomes examined (Table 3), all of which showedevidence of a highly statistically significant trend (i.e. themore vulnerabilities that an individual has, the more likelyit is that they will meet `easeness' on these various measuresof ill health; P<0.0001 for each health outcome).

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Table 3 Vulnerability count according to health outcomes^*

Factor analysis
To aid data interpretation, two factors were generated usinga tetrachoric principal-component factor analysis: factor 1(family relationships) is comprised of not coming from a closefamily, family not doing things together, no family memberto talk to, not feeling valued by family, being hit by parent or caregiver, seeing/hearing parents fight, parents with drugor alcohol problem and being shouted at when young. Factor2 (externalising behaviours) is comprised of being expelledor suspended from school, being involved in fights at school,being in trouble with the police and playing truant. Factors were then divided into tertiles, with the highest tertile representingthose with the highest factor scores. Associations betweeneach factor and the various health outcomes were examined inthe same model since the correlation between the two factorswas relatively low (r=0.3252), despite being highly statisticallysignificant (P<0.0001). Furthermore, there was no evidenceof interaction between the two factors on the outcomes examined.

Factors 1 and 2 were, in general, positively associated withall negative health outcomes (Table 4). The `family relationships'factor was highly associated with having chronic fatigue, multiplephysical symptoms, being a current smoker and heavy drinking.The `externalising behaviours' factor was particularly associated with high levels of alcohol consumption and with having chronicfatigue or meeting caseness on the General Health Questionnaire(GHQ; Goldberg & Williams, 1988).

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Table 4 Vulnerability factors according to health outcomes

Vulnerability factors and exposure to trauma
To examine the possibility that those with pre-enlistment vulnerability were at greater risk of adverse health outcomes because ofconfounding (i.e. the possibility that more pre-enlistmentvulnerability meant more exposure to trauma), we examined theassociation of each of the vulnerability factors with exposureto trauma. The `family relationships' factor is highly correlated with trauma (P<0.0001), and there is a clear pattern between increasing exposure to trauma and being in the highest tertilefor this factor. The association with the `externalising behaviours'factor is less clear, although there is still a correlation(P=0.001). In view of this association, we repeated the analyseswith only those with previous deployments (n=5185) with andwithout adjustment for exposure to trauma (Table 5). Adjustingfor exposure to trauma reduced the effect of the `family relationships'factor but had a marginal effect on the associations with the`externalising behaviours' factor.

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Table 5 Vulnerability factors according to health outcomes, restricted to those who have been deployed since 2000 (n=5185)

DISCUSSION

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DISCUSSION

Key findings
Pre-enlistment vulnerability is common in the UK armed forces.Two main factors emerge as important predictors of ill health:a `family relationships' factor, which reflects the home environmentduring childhood, and an `externalising behaviours' factor,which reflects a variety of markers of behavioural disturbanceduring childhood and adolescence. Pre-enlistment vulnerabilityis more common in young single men from lower ranks in the Army with low educational attainment. Pre-enlistment vulnerabilityis associated with a variety of negative health outcomes, includinggeneral psychological ill health, PTSD and self-harming behaviour,heavy drinking and smoking. There was a trend between all healthoutcomes and increasing vulnerability. The `family relationships'factor is associated with increased exposure to trauma, andthis may contribute to the association of this factor with increasedrisk of PTSD.

Childhood adversity and health
The association of childhood vulnerability and poor adult mentalhealth outcomes reported here has been reported previouslyin the general population (Brown & Harris, 1993; Kessler et al, 1997; Molnar et al, 2001). A series of studies using a similar rangeof measures of childhood adversity has shown a clear and gradedassociation between these measures and other negative healthoutcomes, such as heavy alcohol use, smoking, illicit drug use,poor physical health, increased mortality and attempted suicide(Anda et al, 1999, 2002; Dube et al, 2001, 2003a,b).

Vulnerability and the UK military
Historically, the UK armed forces have recruited from inner-cityareas with high levels of socio-economic deprivation and socialproblems (Johnstone, 1978). Individuals growing up in suchareas have often been exposed to many of the vulnerability factorsknown to contribute to a variety of poor outcomes in adult life (Stewart-Brown et al, 2002).

The finding that such vulnerabilities are common and more prevalentamong those who are young, from the Army and from lower ranksconfirms anecdote, although we believe that this is the firsttime that it has been documented by an epidemiological study.It has been suggested that such individuals often join up to`escape' from adversity at home such as physical abuse or marital discord between parents. The decision to make a career in thearmed forces may also select for individuals with personalitytraits, such as sensation-seeking and impulsivity, and thesetraits are also likely to be associated with pre-enlistmentvulnerability (Brodsky et al, 2001).

Childhood adversity and PTSD
The association of early adversity with PTSD is of particularinterest. A previous meta-analysis has revealed that adversityin childhood, including experience of prior trauma and psychopathologyin a parent (including alcohol dependence), is associated withan increased risk of PTSD after exposure to subsequent trauma(Ozer et al, 2003).

Previous work suggests that early adversity may predispose anindividual to PTSD by a `double hit': not only are they aremore likely to develop PTSD with any given traumatic exposurebut they are also more likely to be exposed to trauma in acombat situation (Helzer et al, 1987; King et al, 1996). Thisfinding is replicated here. This may be explained by the factthat adversity in childhood and adolescence is associated withrisk-taking/impulsivity, poor self-regulation and sensation-seekingin adult life, and such personality traits predispose an individualto be exposed to combat (King et al, 1996).

The relationship between these risk factors, risk of exposureto traumatic events during combat, other more proximal factors(for example social support, morale within the unit and currentpsychopathology such as anxiety or depression), and subsequentPTSD will be explored in a subsequent publication.

Limitations
Response bias can be a special problem for sensitive questionswithin a larger questionnaire, although there was no differentialresponse bias for these questions (data available from authors).Retrospective recall of childhood experiences, particularlyadverse ones, is vulnerable to recall bias (Maughan & Rutter, 1997). Robins et al (1985) tested recall of family environments inadults by comparing their responses with siblings of a similarage. He found that recall was reliable and valid, and was notinfluenced by whether the person had a psychiatric disorderor not. Furthermore, questionnaire ratings of early parentingexperiences show good stability over a 20-year period (Wilhelm et al, 2005).If there is a systematic bias, most studies suggest that peopletend to underreport such experiences as adults (Lewis et al, 1989; Della Femina et al, 1990).

A limitation of our study is that we do not have comparativedata from the general population. We are therefore unable tocomment on the prevalence of these factors in the militaryin comparison to a similar age-matched general population,or to compare their contributions to ill health in the two groups. It may be possible to address such questions by linking ourcohort with a contemporaneous general population cohort whichhas been questioned about similar vulnerability and healthoutcomes.

Implications
How could this information be used in a meaningful way? Ourgroup have argued that there is no benefit in the routine screeningof either new recruits or prospective combatants, as our abilityto predict who develops PTSD is poor (Rona et al, 2006). Asidefrom the practical considerations of the stigma of raisingthese questions within the setting of military culture, noneof these factors have sufficient precision to be used to prospectivelyidentify individual personnel likely to develop PTSD. Also,what this analysis does not tell us is the reverse side ofthe coin – the numbers of equally `vulnerable' personnelwhose social and psychological trajectories have been improvedby the strong sense of identity, career structure and socialsupport that the military provides.

We therefore categorically do not suggest that these resultsshould lead to a principle of excluding recruits from vulnerablebackgrounds. Instead we argue that it is important to recognisethat some individuals have pre-enlistment histories which makethem more vulnerable to psychological problems. Therefore itshould remain a priority for the military as an employer tocontinue to develop appropriate support systems for all personnel during their service.

REFERENCES

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