Depression is an important global public health problem, in part, because of its high lifetime prevalence 1, and its association with poverty, malnutrition, and debilitating chronic disorders including angina, arthritis, diabetes, chronic headaches and migraines 12. Several investigators have documented associations between depression and outward anger expression 345. Collectively, available evidence suggest that aggressive, outward violent behavior is associated with an increased risk of symptoms of depression 67. Motivated, in part, by the high prevalence of violence among youths 8 and increasing awareness of the increasing burden of anxiety and depressive disorders among youths 9, investigators have begun to evaluate associations of anger coping styles, violent behavior, and symptoms of depression among youths 10111213. Goodwin 10, in her analysis of data from a health behavior survey of US school-aged children, noted that outward anger expression was associated with an almost 3-fold increased risk of feelings of depression among boys. Similar positive associations between anger expression with symptoms of depression have been reported by others including those who studied male Japanese students 14, as well as Turkish and American female students 13. In Iceland, Gudlaugsdottir and colleagues 15 documented associations between violent behavior and negative life events. Additionally, Orpinas et al 16 noted that students exhibiting violent behaviors in schools (e.g., involved in physical fights, carried a weapon to school) were more likely to have symptoms of depression than students not exhibiting such behaviors. To date, few studies evaluated associations of violent behavior, anger coping styles, and symptoms of depression among African youths. Available data, although scarce, from studies conducted among Ethiopia youths 171819 suggest high frequencies of outward anger expression among male college students 19, and high frequencies of feelings of depression among secondary school students 1718. It should be noted that most studies that have evaluated anger expression, violent behavior and depression among college students have primarily been focused on North American and European populations. The extent to which, if at all, inferences from prior studies may be generalizable to African college students is unknown. Notably, investigators have reported that social environments and cultural backgrounds are important determinants of how depression is experienced and expressed in psychological, emotional, or physical terms 20212223. Given the scarcity of studies involving African youths and the need for evidence based cross-cultural understanding of expression of emotions, we used data from a previously completed survey 19 to evaluate the extent to which outward anger expression and violent behavior are associated with symptoms of depression among Ethiopian male college students.

Some 23.6% (277 of 1,176) of students in this study population had symptoms consistent with some degree of depression during the current academic year. Only a small fraction of students had symptoms consistent with moderately severe (75, 6.4%) or severe (27, 2.3%) depression. These prevalence estimates of students with symptoms of depression are similar to those reported elsewhere 33. Demographic and lifestyle characteristics of students with no symptoms of depression versus those with symptoms of depression are summarized in Table 1. Students with depressive symptoms were more likely to report khat use, alcohol consumption and cigarette smoking, though only the latter behavior reached statistical significance. Students with depressive symptoms were more likely to report witnessing parental violence as a child and to have 3+ negative life events during the academic year. Students with and without depressive symptoms were similar with respect to age, college level, religious affiliation, and childhood residence.

The mean anger-out expression score was 12.9 (standard deviation 3.9) (table not shown). Overall, 67.8% of students were classified as having a moderate or high outward anger expression (797 of 1,176). Notably, 29.3% (344 of 1,176) of students were classified as having a high (anger-out score ≥ 15) level of outward anger expression. These values are consistent with reports from other populations 101214.

Anger expression and reports of violent acts were both positively associated with the presence of depressive symptoms among students in our study populations (Table 2). Students with moderate outward anger expression (score: 11–14), were 2.03-times more likely to have depressive symptoms (OR = 2.03; 95% CI 1.40–2.95) as compared with those students classified as having low outward anger expression (score ≤ 10). Students with high (≥ 15) anger expression were 3.75-times more likely to have depressive symptoms as compared with their counterparts with low anger expression (OR = 3.75; 95% CI 2.58–5.44). Moderate (adjusted OR = 1.97; 95% CI 1.33–2.93) and high (adjusted OR = 3.23; 95% CI 2.14–4.88) outward anger remained statistically significantly associated with the presence of depressive symptoms after we controlled for confounders.

We also evaluated the extent to which, if at all, violent behavior was associated with symptoms of depression. As can be seen in table 2, in bivariate analyses, violent behavior was associated with depressive symptoms (unadjusted OR = 1.82; 95% CI 1.37–2.40); however, the association was greatly attenuated, and became statistically insignificant after adjustment for confounding variables (adjusted OR = 1.12; 95% CI 0.82–1.45).

Next we evaluated frequencies of different types of outward expression of anger (Table 3). Students in the present study were most likely to "verbally express their anger" to others (70.2% responded sometimes, often, or almost always); and were apt to "tell someone if annoyed" by them (66.2%) (Table 3). Students were less likely to report "striking out" when angered. The following specific outward expressions of anger were found to be statistically significantly associated with depressive symptoms: "slamming doors" (OR = 1.88; 95% CI 1.40–2.52), "arguing with others" (OR = 1.63; 95% CI 1.22–2.19), "striking out at whatever infuriates" (OR = 2.43; 95% CI 1.78–3.31), "saying nasty things" (OR = 2.06; 95% CI 1.52–2.78), and "losing temper" (OR = 1.78; 95% CI 1.34–2.41) (Table 4).

The results of our study provide support for the hypothesis that high levels of outward anger expressions are significantly associated with symptoms of depression. In contrast, violent behavior was not significantly associated with symptoms of depression. These findings are in general concordance with results reported in other studies 103435.

In this study, moderate and high anger-out expression scores were associated with a 2.18-fold and 3.38-fold increased risk of having depressive symptoms respectively. These results are generally consistent with findings reported by others. Goodwin, in a survey conducted among US youths10, reported that outward anger expression was associated with an almost 3-fold increased risk (OR = 2.8; 95% CI: 2.5–3.1) of experiencing symptoms of depression among boys. Sperberg et al, in their study of 223 female college students noted that anger-out was positively associated with symptoms of depression (Pearson's Correlation Coefficient = 0.23; p < 0.01), and that the association remained significant even after adjusting for potential confounding variables 34. Similarly, Lee and colleagues, in their study of Korean cancer patients, reported a positive association between outward anger expression and symptoms of depression (Pearson correlation coefficient = 0.240, p = 0.001) 11.

Our results and those of other investigators working in this area, however, are not consistent with findings from a recent study in Japan 14. Kitamura and Hasui 14, in their study of 457 students reported that outward anger expression was not associated with depression (Pearson's correlation coefficient = 0.083). However, careful examination of results from their multivariate analysis suggested a statistically significant inverse association between outward anger expression and symptoms of depression (β = -0.163, p < 0.01).

The results of our study indicate that although violent behavior was associated (OR = 1.82; 95% CI 1.37, 2.40) with symptoms of depression in univariate analysis, the relationship was greatly attenuated (OR = 1.08; 95% CI 0.73, 1.60) when other covariates were included in multivariate models. Reports pertaining to association between violent behavior and symptoms of depression have been inconsistent. Salmon et al, in their study among 904 UK secondary school students reported that adolescents with violent behavior acts were 3.3-times more likely to report symptoms of depression (OR = 3.3; 95% CI 1.6–6.7) 7. Similarly, in Finland, Kaltiala-Heino et al found that those who reported frequent violent acts were associated with a 2.8-fold increased risk (OR = 2.8; 95% CI 2.2–3.7) of experiencing symptoms of depression 6. Inconsistencies across studies may be attributable to differences in population characteristics, type of study design, types of instruments used to assess violent behavior and symptoms of depression and variations in socio-cultural characteristics across study populations. Clearly more studies, particularly those that apply uniform sampling and assessment methods are warranted to move this area of literature forward.

Symptoms of depression, outward anger expression and violent behavior acts have been found to differ within cultural contexts and experiences 133637. More research is needed to identify the specific cultural characteristics of our study population and to deduce how certain cultural elements might influence students' outward expression of anger as a manifestation of depression.

Several limitations must be considered when interpreting the results of our study. First, the cross-sectional design of our study does not allow for conclusions to be formed about causality. For instance, although an association exists between negative life events and depressive symptomology, we cannot necessarily support the intuitive notion that the onset of depression spurs from negative experiences; perhaps depressed youth adopt a cognitive style in which they interpret all life events in a more negative light 38. Second, our study population was exclusively comprised of young male participants who were currently attending college, thus conclusions cannot be generalized to all males (e.g. children, adults, college drop-outs), all college students (e.g. female), or other broader populations (e.g. all students in East Africa). Third, the instruments used to assess anger expression and symptoms of depression are not comprehensive. Our study exclusively dealt with Spielberger anger-out expression. Future studies should include other dimensions of anger expression such as anger-in and anger-control. Additionally, we used the PHQ-9, an instrument not previously validated in the present study population, to assess depressive symptoms. The PHQ-9 instrument, however, has been used widely to estimate prevalence of depressive symptoms in community-based settings around the world39. Investigators have reported that the measurement of depression in international contexts may be undertaken with similar instruments in different cultural settings, provided care is taken to ensure an adequate translation and validation of the cut-off score40. Along these lines, investigators have shown that the PHQ-9 can be used in the African context 4142. Adewuya and colleagues 41 in their study of Nigerian university students reported that the PHQ-9 is a valid and useful instrument in screening for depression in their settings. Additionally the PHQ-9 has been used successfully by Omoro and colleagues 42 in their study of Kenyan cancer patients. Fourth, the present analysis is limited in that we were not able to quantify the mediating and interactive effects of anger expression and depression on the occurrence of violent behavior. Finally, our study focused on violent behavior perpetrators and did not include victims of violence. Although the adverse health outcomes on victims of violent behavior has been well established, future studies that investigate the independent and joint associations of both perpetrators and victims of violent behavior and adverse social and mental health outcomes are needed.

In summary, outward anger expression was positively associated with symptoms of depression among male Ethiopia college students, a population that has been rarely studied, despite the high prevalence of violence in Ethiopia and other parts of Africa 84344. From a public health perspective, these data suggest that outward anger expression, perhaps more than violent behavior, may be useful as a means to identify students at increased risk of depression and depressive symptoms. Our findings expand the existing literature and underscore the global significance of links between outward expression, violence and depressive symptoms. The high prevalence of violence 844, depression 1 and outward anger expression 14 among male college students is particularly important given that they are likely to assume leadership positions important in influencing the future economic, political, and socio-cultural fabric of their respective communities. Further research should be conducted to better characterize community and individual level determinants of anger, violent behavior and depression among youths. Results from such research should then be used to develop school-based intervention programs and treatment programs designed to reduce violent behavior and promote appropriate anger expression skills among adolescents and young adults.

The authors declare that they have no competing interests.

Each author participated in the design, analysis, and interpretation of results. All authors contributed to the writing or editing of this manuscript.