Present study participants with clinically verified MetS had a significant higher score for depression, anxiety, and distress. This study showed individuals with MetS had impaired QoL.
Current study suggested the association between MetS and depression. In line with our findings, a community-based study [23
] found that MetS is associated with self-perceived depression. In a cohort study [24
], MetS could predict depression. While another research [5
] on depressed patients indicated the association of long-term depressive symptoms and emergence of MetS, Räikköonen et al. [6
] have shown in their study that psychological factors play causal role in MetS. Hence, it seems there is a two-way street between depression and MetS.
In spite of different study methods, our results are in agreement with Räikkönen et al. [25
] and Carroll et al. [26
] and showed that anxiety is associated with MetS in both sexes. Other findings of Räikkönen's studies demonstrated that feeling intense, anger, and distress increased risk for MetS [6
]. Furthermore, other researchers [8
] have suggested emergence of MetS after 5 years exposure to high psychological distress. Statistically significant association of our participants' distress with MetS was lost after adjusting for BMI, smoking, age, sex, and cholesterol level. Different measurement methods of psychological distress, type of research, study population, and adjusting factors in present study compared to Räikkönen et al. researches may justify these differences.
Our findings showed that individuals with MetS had impaired QoL in terms of health, mobility, self-care, usual activity, pain/discomfort, and anxiety/depression, even after controlling confounding factors. Two different studies [9
] have demonstrated that people with MetS have impaired QoL including physical and social function as well as general and mental health. Although studies about QoL and MetS are few, but present study findings were in accordance with them and have suggested impaired quality of life in patients with MetS.
Some mechanisms were suggested as possibly responsible for association of psychological disorders, impaired QoL and MetS. First mechanism is biological alternation [27
] such as autonomic nervous system changes like heart rate variability, dysregulation of endocrine organ like hypothalamic-pituitary-adrenal axis, and alternation of inflammatory and hemostatic markers and neurotransmitters especially blunted level of serotonin [6
]. Second mechanism is separated correlation of psychological problems with MetS components, for instance, association of depression with visceral fat accumulation, insulin resistance, and dyslipidemia [2
]. Last one is the similar risk factors of psychological, and metabolic disorders [9
], for example, low intensity of leisure time physical activity, unhealthy dietary habits, high consumption of alcohol, and low education, and so forth.
This study benefited from participants with wide range of age, enough sample size, and recruiting individuals who had MetS for about 7 years. However, some limitations should be considered. First, self-reported questionnaires such as HADS give limited data about participants' depression and anxiety at one time but no information about lifetime psychological problems. Second, in spite of wide level of adjustment in analyses of present study, it is still possible that unmeasured confounders interfere with part of the association between MetS and psychological disorders. Third, recall bias may occur because participants with MetS may report poorer social and emotional situation because of the syndrome. In addition, cross-sectional design of study makes temporality problem that causes difficulties in interpretation of cause and effect.