Based on the findings of the present study, controlling for the association of lifestyle factors (smoking, nutrition practice, and physical activity) and demographic characteristics (place of residence, gender, age, income levels, education levels, occupation, and marital status), it was observed that stressful life events including family problems, job insecurity, financial problems, and social relations directly were associated to level of perceived stress. Among the proposed stressful life events, family and social problems had more notable relation with stress perception. This may be related to different Iranian cultural aspects that people are more sensitive to familial and social (engagement) relationships. In accordance with our study, in Sapr ÜNER and colleagues' study on student subjects, direct relation was observed between mental health which was measured by the GHQ-12 and stressful life events including lack of positive events during the past year (OR = 1.32), emotional violence (OR = 1.65), a poor relationship with father and mother (OR = 1.57 versus 1.7, resp.), and poor relationship with partner (OR = 2.29) [22
]. Also, some other previous studies have found strong association between psychosocial stressors and mental disorders [32
]. In a longitudinal study, Stanfeld et al. studied 7977 individuals and concluded that the higher score of stress was correlated to low social support, in men (OR = 1.31) and women (OR = 1.17) while controlling for stress score at the baseline, age, and place of work [23
Stress-related side effects of job insecurity and other sources of job stress and career dissatisfaction on people's mental health and other important aspects of their overall well-being have been investigated in previous studies [51
]. Previous studies suggested that fulfilling one's need for security and stability may be regarded as more important than the job itself, in which one's overall engagement may be impacted or lowered until one's basic need for security or psychological safety has been satisfied [24
We found an independent association of financial conflicts with reported levels of perceived stress after adjusting for potentially confounding individual variables; however, its magnitude compared to other stressors was smaller. In line with our research, earlier studies showed that the experienced financial problems concurrently predicted psychological distress [53
Although in current research being a smoker had positive impact on more perception of stress, it was not statistically significant. Majority of previous studies that studied the relation between stress and smoking have predominantly shown that smokers report higher stress levels than nonsmokers; according to the observation of higher stress in smokers versus nonsmokers, it was concluded that smoking causes stress [54
For both men and women, high levels of perceived stress were associated with higher GDI score. In accordance with our study, several studies have obtained similar conclusions [57
Our results in line with Debbie et al. showed that the high level of physical activities was associated with perceived stress reversely [30
]. As can be seen from , low or moderate level of physical activities weakly associated with experiencing low levels of perception of stress. Previous studies on the relationships between stress and physical activity have produced mixed results. In some of these studies, no relationship was approved and some of them concluded that chronic physical activity reduces stress and improves its symptoms [60
Some studies have suggested that the effects of stress on health outcomes are different for men and women, which may be explained by sex differences in vulnerability, stress response, or coping strategies [14
]. Compared with women, men seem to respond to stress with greater reactivity of the hypothalamic-pituitary-adrenal axis, which may partly explain the observed sex differences [64
In current research, it was observed that the married people more affected by stressors than singles particularly over the right tail of distribution of perceived stress; however, marital status was not significantly correlated with stress perception in majority of quantiles. Such a result can be justified by the fact that married people are generally more concerned about their situations because of their responsibilities toward the family.
According to values of regression coefficients, it can be inferred that the income level was one of the stronger predictors of perceived stress particularly over the less than 80th quantile. The association of income level with perceived stress was most pronounced among those whose incomes were in (300–500$) and >=500$ (i.e., middle and high income levels, resp.). Our findings support the conclusions of some earlier studies [13
] and are not consistent with those that supporting the limited resources have a direct negative impact on quality of life and health [67
In the current study, indirect association was observed between education levels and perceived stress. This means that there was a positive relation between high education level and adaptive coping strategies (less affecting by stressors) and a negative relation between low education level and maladaptive coping strategies (more affecting by stressors). For instance, the odds of perceived stress for people with academics attainment at 15th quantile was 0.34 (0.16 and 0.27 for people were in 1–8 and 9–12 years of education, resp.) times less than illiterates while at 95th quantile it was 0.52 (0.31 and 0.38 for people were in 1–8 and 9–12 years of education, resp.), resulting that the individual adaption are affected by education level, in which higher educational qualifications had notable positive role in more stressful situations. Educational level creates differences between people in terms of access to information and the level of proficiency in benefiting from new knowledge [12
]. Accordingly, a lower education placed people at a disadvantaged position for majority of the stressors (i.e., financial stress, worse perceived health status, and psychological distress) and resources (i.e., perceived life control, social support, and social cohesion) [68
]. Majority of the previous research on the relationships between perceived stress and education level have produced consistent results and supported our findings [33
Regarding to the relation of age with perceived stress, present study showed middle-aged (30–50 yrs) and elderly people similarly less affected by stressors than young people, although majority of the estimated coefficients over whole distribution of outcome variable were not statistically significant. The reported relation of perceived stress and age in most recent previous studies [6
] was in contrast with our findings. This difference may be attributed to socioeconomic status of Iranian society that the young people more faced with high levels of stress due to financial problems and job insecurity.
4.1. Study Strength and Limitations
Strengths of the current study included a large community-based sample and assessment of the relations of multiple stressors that were not considered in earlier studies and most important life style behavior variables, that is, food intake, physical activity, and tobacco use using comprehensive statistical method. Limitations included cross-sectional analysis, in which causal inferences cannot be made. Another limitation was that the dependent variable and majority of behavior measures were subjectively assessed daily and monthly; accordingly, they may be subjected to social preference or memory bias. Other limitation of this study was the ignoring of mediator role of some variables such as health behaviors and educational level that influence people's level of stressors and resources; accordingly, developing a structural equations modeling in this context could be considered as an effective approach.
The present paper was an M.S. thesis in biostatistics at School of Health, Isfahan University of Medical Sciences, project number: 390248.