Post-traumatic stress disorder and alcohol misuse: comorbidity in UK military personnel

This study uses data gathered as part of Phase 2 of the health and well-being survey of serving and ex-serving members of the UK Armed Forces [38, 40]. This study collected data via self-complete questionnaires. Phase 1 of the survey was carried out between 2004 and 2006 [40], assessing the physical and mental health of the UK Armed Forces, comprising two samples. The first, termed the TELIC sample (the codename for the 2003–2009 UK military presence in Iraq), included personnel who deployed to Iraq between January 18, 2003, and April 28, 2003, and consisted of approximately 10 % of the fighting force deployed at that time. The second group, termed the Era sample, comprised individuals who were in the military during the same period, but were not at that time deployed to Iraq. In total, 10,272 participants completed the Phase 1 questionnaire (response rate 59 %).

Phase 2 of the survey used a modified version of the Phase 1 questionnaire, with data collection occurring between 2007 and 2009. Participants from Phase 1 were re-contacted, with 6429 individuals (response rate 68.4 %) completing the Phase 2 questionnaire (now termed the follow-up sample). Two new samples were also included. The first was a random sample of personnel deployed to Afghanistan on operation HERRICK (the UK military codename for operations in Afghanistan) at any time between April 2006 and April 2007. 896 individuals (response rate 50.1 %) in this sample completed the Phase 2 questionnaire. The second new sample, termed the replenishment sample, included individuals who had joined the military since recruitment for Phase 1 in 2003, and had the opportunity to deploy on either TELIC or HERRICK during the study period. This sample was randomly drawn from those who joined the trained strength between April 2003 and April 2007, and 2665 individuals (response rate 40.2 %) completed the questionnaire. In total, 9990 individuals completed the Phase 2 questionnaire (overall response rate 56.0 %). Of these, six were later removed as they were found to be ineligible, resulting in 9984 individuals in the final sample (Fig. 1).

The socio-demographic characteristics of the Phase 2 sample were compared with the composition of the UK military (at April 2007), to ensure the sample was representative [38]. The distribution of sex, age, engagement type and rank was similar between groups, with service being the only exception; the sample included proportionally more army personnel than the UK military as a whole in 2007 (67 and 56 % respectively).

All participants were identified by Defence Analytical Services and Advice (DASA), UK Ministry of Defence (MoD), and ethical approval was provided by the King’s College Hospital local research ethics committee, and the MoD Research Ethics Committee (MODREC).

To assess alcohol misuse, the Phase 2 questionnaire utilised the 10-item World Health Organization (WHO) alcohol use disorders identification test (AUDIT) [41]. The AUDIT assesses levels of alcohol consumption, alcohol dependence and negative consequences of alcohol abuse, in the previous 12 months. For the purposes of this study, participants were classified as reporting ‘alcohol misuse’ if they scored 16 or above. This cut-off is higher than that commonly used in the general population, and is defined by the WHO as ‘hazardous use that is also harmful to health’ [41].

For the assessment of PTSD symptoms, the Phase 2 questionnaire used the National Centre for PTSD Checklist—Civilian version (PCL-C) [42]. This is a 17-item questionnaire, and a cut-off of 50 or more was used to define caseness (‘probable PTSD’). Each question is rated on a scale from 1 to 5 depending on how often the individual has ‘been bothered by these problems’ in the past month, with 1 being ‘not at all’ and 5 being ‘extremely’.

The PCL-C can be divided into three PTSD symptom clusters [43], with 5 of the 17 questions assessing ‘re-experiencing’, 7 ‘avoidance’, and 5 ‘hyperarousal’ symptoms, corresponding to DSM-IV diagnostic criteria [44]. A rating of 4 or above (indicating the participant has been moderately bothered by that problem in the past month) was considered a positive response for that symptom being present. In order to determine caseness for the three symptom clusters, the following criteria were used: the ‘re-experiencing’ cluster required 1 or more positive symptom responses, the ‘avoidance’ cluster 3 or more positive symptom responses and the ‘hyperarousal’ cluster 2 or more positive symptom responses [43].

Symptoms of common mental disorder (CMD) including somatic symptoms, anxiety/insomnia, social dysfunction and depression were measured using the General Health Questionnaire 12 (GHQ-12) [45]. This assessed symptoms of CMD in ‘the last few weeks’, with caseness defined as a score of 4 or above (out of a possible 12) [46].

Two measures were used to assess childhood adversity [47], which were adapted from the Adverse Childhood Exposure study scale [48]. The first measured childhood family relationship adversity, by means of four positive items that were negatively scored (e.g., “I came from a close family”), and four negative items (e.g., “I used to be hit/hurt by a parent or caregiver regularly”) [47]. The scores for these eight items were summed to form a cumulative measure, and analysed as 0, 1 or 2+ adversities. The second measure assessed childhood antisocial behaviour, and was deemed positive if the participant a) answered ‘true’ to “I used to get into physical fights at school”, and b) answered true to one of the following: “I often used to play truant at school”; “I was suspended or expelled from school”; or “I did things that should have got me (or did get me) into trouble with the police” [49].

Age at Phase 2 questionnaire completion (in years), sex and marital status (single; married/cohabiting/in a relationship; separated/widowed/divorced) were assessed, as well as rank (commissioned officers; non-commissioned officers and other ranks), engagement type (regular or reservist), most recent deployment (Iraq; Afghanistan; no deployment) and whether the individual deployed in a combat role.

The majority of participants were male, in a relationship, under the age of 40 years, regulars of non-commissioned officer (NCO) or other rank, and more than half reported no previous deployment to either Iraq or Afghanistan (Table 1). A quarter of the sample reported that they were in a combat role in their parent unit. More than half of the sample reported at least one family relationship adversity in childhood and 17 % met the criteria for childhood antisocial behaviour. A fifth of the sample met the criteria for a CMD and 4 % met criteria for probable PTSD.

376 participants [4.0 % (95 % CI 3.5–4.5)] were defined as having ‘probable PTSD’, with 1323 participants [13.0 % (95 % CI 12.3–13.8)] defined as reporting alcohol misuse. 1.8 % (95 % CI 1.5–2.1) of participants (n = 159) scored above threshold on both measures, and 84.8 % (95 % CI 83.4–85.6) did not score positive for either condition (n = 8251). In the group reporting probable PTSD, 44.9 % (95 % CI 0.4–0.5) had comorbid alcohol misuse, and within the group defined as reporting alcohol misuse, 13.6 % (95 % CI 0.1–0.2) also reported probable PTSD.

Rates of probable PTSD were assessed in those who scored positive for alcohol misuse, and those who did not. Those scoring positive for alcohol misuse showed an approximate threefold increase in odds of having probable PTSD, compared to those without alcohol misuse (Table 2).

All three PTSD symptom clusters were significantly associated with alcohol misuse compared to those without alcohol misuse, with a two- to threefold increase in odds for each cluster (Table 2).

The association between probable PTSD and various socio-demographic and military factors were examined in the group meeting the criteria for alcohol misuse. Individuals aged 30–34 years, and those aged 40–44 years, showed an approximate two- to threefold increase in odds for probable PTSD (compared to the reference category of participants aged 18–24 years) (Table 3). Officers had reduced odds of PTSD compared to non-commissioned officers and other ranks. Participants who were in a combat role in their parent unit showed a twofold increase in odds compared to participants in a non-combat role. The most strongly associated factor was CMD, with individuals scoring positive for CMD showing a 20-fold increase in odds for probable PTSD compared to those who did not. This may to a large extent be explained by the strong association between PTSD and CMD (results available from authors).

Most studies looking at PTSD and alcohol misuse in military populations have focussed on the US Armed Forces, and by drawing data from the UK military, this study has broadened the scope of research in this field. This study also investigated the three symptom clusters of PTSD separately, a distinction not made in all research. Furthermore, although all data were gathered using a self-report method, the measures included in the questionnaire (e.g., AUDIT, PCL-C) have well-established reliability and validity.

There are various aspects of the association between alcohol abuse and PTSD that are not addressed in this study. Although we have looked at the prevalence of PTSD in those scoring positively for alcohol misuse, the low overall prevalence of participants scoring positive for probable PTSD prevented us from having the statistical power to investigate what factors were associated with alcohol misuse in the PTSD group. Also, some studies separate the ‘avoidance’ cluster of PTSD symptoms into two groups—‘avoidance’ symptoms and ‘numbing’ symptoms—and they suggest it is the ‘numbing’ symptoms that are more strongly associated with alcohol misuse [67, 68]. By not dividing the ‘avoidance’ cluster this association could potentially be missed. This distinction was not made in the present study, due to the low reported prevalence of PTSD in our sample. Further this study was based on the DSM-IV criteria for PTSD using the PCL. Recently with the introduction of the DSM-V criteria, the three symptom clusters (intrusive recollections, avoidant/numbing symptoms, and hyper-arousal symptoms) have been replaced by four symptom clusters (intrusion, avoidance, negative alterations in cognitions and mood, and alterations in arousal and reactivity). It will be essential that the revised criteria are explored in subsequent studies which use the PCL-5.

Although the majority of military personnel do not report alcohol misuse or PTSD, this study has demonstrated that PTSD and alcohol misuse do co-occur with approximately 50 % of those with probable PTSD also reporting alcohol misuse. This has implications for clinicians who should ensure that individuals presenting with either condition are assessed for comorbidity. Therefore, treatment for PTSD should take the alcohol misuse into account rather than treating the conditions consecutively. This might help identify the cause of their initial presentation (e.g., heavy drinking to alleviate the symptoms of undiagnosed PTSD), and in turn lead to more effective treatment and counselling programs. The role of CMD is also important to consider as some individuals reported all three conditions, this level of co-morbidity is likely to impact on presentation and treatment priorities. However, these cross-sectional results do not clarify the direction of the association.