In this study we aimed to examine the impact of socioeconomic disadvantages and exposure to traumatic events on PTSD-depression comorbidity, PTSD, and depression.
The significant association between socioeconomic disadvantage on both PTSD only and PTSD-depression comorbidity is noteworthy. Severe socioeconomic disadvantage was the risk factor with the strongest association to comorbid condition (OR= 8.096). Similarly, the results of our study revealed a dose–response association between exposure to traumatic events, on the one hand, and PTSD only and comorbid condition, on the other hand. Experiencing eight or more traumatic events increased the likelihood of having PTSD only or the comorbid condition. So did the exposure to four or more trauma after the Peace Agreement.
These findings are in agreement with the assumption that, rather than focusing merely on trauma exposure, the effect of socioeconomic conditions on mental disorders need to be emphasized in the post-conflict populations. Following the same line of argument, Miller and Rasmussen  distinguish between war exposure and ‘daily stressors’ as determinants of mental health in the population in war-effected settings. The authors emphasize the role of ‘daily stressors’ (stressful social and material conditions, ongoing adversity, or ecological stressors ), which directly and indirectly, influence the mental health. Acknowledging the role of a wider range of ecological-social factors can provide a better understanding of mental health outcome in the war-effected settings . Although the term ‘daily stressor’ has been criticized for being imprecise which includes a variety of conditions and events , socioeconomic disadvantages in our study may be interpreted as ‘daily stressors’ for the participants.
Studies on the effect of ‘daily stressors’ in post-conflict populations imply that ‘daily stressors’ account for large proportion of mental distress [52–54]. Indeed, Miller and Rasmussen  argue that “level of exposure to daily stressors has consistently been a stronger predictor than direct war exposure on most mental health outcomes”. In Roberts et al.’s  recent study from the urban setting of Juba, South Sudan, variables related to living conditions (such as lack of food, water, and medical care) were associated with lower general physical and mental health. In our study severe socioeconomic disadvantage, in comparison to recent and older trauma exposure, showed a stronger association to PTSD-depression comorbidity. However, recent traumatic events, compared to severe socioeconomic disadvantage, showed greater association to having PTSD only. Although the rate of recent trauma was similar for PTSD only and comorbid groups, the PTSD only group, compared to the comorbid group, reported to have experienced a higher rate of more extreme and dramatic events such as witnessing murder or murder/violent death of family members.
The strong association between trauma exposure and severe socioeconomic disadvantage and comorbid condition, found in our study, adds to the existing knowledge in the field. What is noteworthy in addition, is the vulnerable position of participants with comorbid condition: not only they had experienced high level of traumatic events (comparable to those with PTSD only), but also their distress level (measured by GHQ-28) was significantly higher than those with PTSD only or depression only. A higher level of psychological distress associated with PTSD-depression comorbidity has also been reported in other studies of post-traumatic conditions . For instance, amongst the survivors of an earthquake, psychological distress was reported to be significantly higher in the comorbid PTSD and depression group than in the PTSD only group (assessed using the GHQ-12) . Another characteristic which distinguishes the comorbid group is the strong impact of trauma during the war (older trauma). Participants with history of trauma during the war were four times more likely to have a comorbid condition. Hence, health personnel should be particularly aware of the needs of persons with a comorbid diagnosis, and also of the characteristic pattern of risk factors.
The pattern of risk factors for the comorbid condition and PTSD only were similar to each other but different from pattern of risk factors for depression only. This finding provides some evidence to the notion that PTSD and comorbid PTSD-depression may be undistinguishable constructs. For instance, in O’Donnell et al.’s  study, PTSD and comorbid PTSD-depression emerged as undistinguishable constructs. However, this is not in accordance with other studies where the two conditions emerge as separate construct .
Living in a rural setting also emerged as a risk factor with different characteristics than living in an urban setting: residents of urban areas showed higher risk of having PTSD only and comorbid diagnosis, while rural residency was associated with having depression only. Generally, inequalities exist between rural and urban health care in Africa/low income countries both in regard to access to and utilization of services . However, more research is needed on the South Sudanese context concerning urban/rural health and availability and utilization of mental health services. Being a returnee increased the odds of being in the PTSD only or the comorbid group. Returnees have been considered as a risk group in other studies .
The rate of PTSD and depression varies highly in different post-conflict populations . For instance PTSD and depression was reported to be at 3.7% and 32.6% among population of postwar Jaffna in Sri Lanka , and 42% and 68% in Afghanistan . The rate of PTSD in our sample was consistent with that of Roberts et al.  in Juba, South Sudan (37.6% and 36%, respectively). However, the rate of depression in our study was much lower than in Roberts et al.’s (16% and 50%, respectively). This discrepancy may be due to use of methods: Roberts et al. applied a screening symptom scale (the Hopkins Symptoms Check List-25) but in the present study a structured diagnostic interview was used in order to diagnose depression.
This study demonstrates that it was possible to conduct such a community survey under very difficult circumstances. For example, there was a lack of proper infrastructure, making it difficult to reach some of the sampling areas, and the security situation had to be carefully and continuously monitored. Emergency psychiatric treatment was therefore occasionally provided by the article’s fourth author (a physician). We believe the results, based on the randomized sample of the study, can be considered as generalizable for Greater Bahr el Ghazal States and relevant for other post-conflict settings. The findings, when related to other studies elsewhere in South Sudan [26,28-30], indicate extremely high levels of poor mental health in South Sudan.
This study also had some limitations. Being a cross-sectional study, it cannot provide a cause and effect relationship between the studied demographic and trauma exposure variables on the one hand and PTSD/depression on the other. Furthermore, we used self-report measures in order to assess exposure to traumatic events, which can pose bias in the form of inconsistency in the memory of events . Self-reported measures rely on the participant’s memory and are also prone to be impacted by dominated attitudes toward the themes of study. The use of an additive scale of traumatic events is a simple way of including an indicator of exposure. However, it does not differentiate between the types and severity of the events. Furthermore, although the instruments used in this study have been widely used internationally in different cultural settings and the interviewers were familiar with the socio-cultural setting, no formal socio-cultural validation was conducted.
Living in a polygamous marriage was considered as a socioeconomic disadvantage because the participants in polygamous marriage were more likely to have no regular income, have low monthly income, be unemployed and have low level of education. It also showed unadjusted association with both depression only and comorbid condition (Table 2) (with no significant differences between male and female participants). However, cautions should be exercised about the social status of individuals in polygamous marriage as these may be perceived by the society as economically well off families who can offered a polygamous marriage.
We were not able to formally assess inter-rater reliability. However, attempt was made, through repeated and supervised interview practice, to ensure a satisfactory level of rating-agreement among the interviewers. Despite these limitations, our findings, based on data from a post-conflict setting, contribute to the ongoing debate on the relationship between PTSD and depression.