Major depression disorder (MDD) is also called depression. It is a mental disorder with a variety of clinical manifestations, such as persistent depression. The core symptoms are depression, lack of interest and pleasure, loss of will and behavior, which are called "three low" symptoms (Delgado, 2004).
It has been shown that teenagers with depression express more anger than nondepressed teenagers through family interactions (Nadja et al., 2018). Grant et al. (2018) suggested that anger is related to depression and tends to occur at the same time. Another study showed a moderate relativity between anger and depression (Christine & Wendy, 2018). Mohammad et al. (2013) found that there is a positive correlation between anger and depression in patients with clinical depression through a questionnaire survey of patients with MDD.
Previous studies have shown a positive correlation between anger and depression (Liliana et al., 2019). Many studies have found that there is a close relationship between anger and depression, so it is often in the form of "codisease" (Grant et al.,2018; Liliana et al., 2019; Mohammad et al., 2013; Nadja et al., 2018). However, depression is heterogeneous, so there may be multiple variables affecting it (Besharat, M. A., Nia, M. E. & Farahani, H., 2013). It is speculated that the components of anger may have a direct or indirect effect on depression with other variables. Some studies have shown that anger is related to sources of mental stress. (Amanda et al., 2015).
Beck & Alfird (2021) considered that depression can be divided into two categories, endogenous depression and reactive depression, according to different internal and external factors. Endogenous depression is mainly caused by internal psychological factors (such as Strait anger), while reactive depression is caused by external stress. Stepanichev M. Y. et al. (2016) considered that severe acute stress events or mild chronic stress factors may induce depression. In an animal experiment, male Wistar rats were exposed to two different chronic stress modes. The levels of cortisol and passive floating behavior in brain tissue and blood were measured, which further aggravated the depressive symptoms. Reactive life stress events are the direct factors leading to depression.
According to the epidemiological statistics of depression, age and gender also have a significant impact on depression (Shan H., Duo S.& Wei Y., J., 2020). Therefore, we explored the different effects of variables such as trait anger, life event stress, depression and gender with age as the moderator of depression. It is particularly important for the pathogenesis of depression, the choice of treatment path and the secondary prevention strategy of the disease.
2.1 The mediating effect of trait anger on depression with life events as a mediating variable.
Anger is a negative emotional state with changing intensity and persistence that is usually associated with emotional arousal and perception of the outside world (Kassinove &Sukhodolsky,1995). Spielberger (1988) showed that state trait anger theory divides anger into state anger, trait anger and anger expression. Trait anger is defined as the tendency of stable desituational anger within the individual, which is a lasting and stable personality trait in the frequency, duration and intensity of anger. Individuals with higher levels of trait anger are more likely to feel enraged in a variety of situations, so they are more likely to experience state anger. Trait anger plays a certain role in the clinical manifestation of depression (Wenze, Gunthert & Forand, 2009).
Therefore, it is inferred that trait anger is an endogenous factor of depression.
Rick E. I. et al. (2007) highlight possible ways in which anger leads to stress directly, with increasing anger and hostility leading to problematic interpersonal interactions. Anger can activate the autonomic nervous system to increase psychological stress sensitivity and activate the adrenal cortex to secrete cortisol through the hypothalamus-pituitary-adrenal axis (HPA) (Mustafa A. U., Stephan B. & William R. L. 2020). The increase in cortisol reduces the recognition of anger in patients with depression and produces more anger than normal people in the field of endocrine research, in which corticosteroids are used as marker variables for the effects of mental stress on depression (Katie &Richard, 2012). Higher anger is accompanied by an increase in cortisol with increased stress, and it is speculated that there is a positive correlation between the increase in mental stress and anger in depressed subjects. However, Amanda et al. (2015) found different results that showed that greater anger was associated with less cortisol output when they investigated the relationship between daily cortisol and anger in depression. Ellen et al. (2019) further found that the slowing of the daytime cortisol slope may have a protective effect on some forms of internalized psychopathology and relieve depressive symptoms in highly irritable cases, in which the effects of circadian rhythms of cortisol diurnal patterns on irritability lead to internalization and externalization symptoms in children 9 years later. Joana S.C. P et al. (2020) explained that participants with trait anger showed the highest level of HPA activation in response to stressors, which activates hypothalamic paraventricular nucleus neurons (PVN) to secrete arginine vasopressin (AVP) and corticotropin releasing factor (CRF), which in turn promotes the production and secretion of adrenocorticotropin (ACTH) in the anterior pituitary. Therefore, ACTH induces the production and secretion of corticosteroids and glucocorticoids (corticosterone). Cortisol enters the bloodstream from the adrenal cortex. Therefore, high levels of cortisol inhibit the further release of ACTH and CRF through a negative feedback mechanism with the binding of cortisol to glucocorticoid receptors (GRs) in the pituitary, hypothalamic paraventricular nucleus and hippocampus. This results in a return to the physiological state after acute activation of the system. In the case of depression, the negative feedback loop of the HPA axis is damaged, leading to a long-term increase in glucocorticoids (JoanaS.C.P.et al.,2020). It is precisely because the negative feedback mechanism of cortisol is impaired in patients with depression when they feel angry and the level of cortisol in the blood cannot return to a low level that life stress events lead to maladjustment. Maladjustment of stress can lead to disorders of the HPA axis and the immune system. Furthermore, it leads to cognitive and emotional disorders, thereby increasing the risk of depression (J.S. Cruz-Pereira et al., 2020).
Rick E.I. et al. (2007) considered that anger tends to increase sensitivity to life events, which is the core feature of depression. Sensitization is also a necessary condition for depressive disorder (Scott B.P., 2008).
There was a significant positive correlation between stressful life experience and depression (Rannveig, Bryndis, Sarah &Inga, 2017). Therefore, mental stress is regarded as a major factor leading to depression (Maheenetal. 2019). Beck's model suggests that depression follows when stressful life events activate negative schemata, including dysfunctional attitudes (Beck A.T., 1987). Kai G. R. et al. (2022) showed that there was a negative correlation between stressful life events (SLEs) and gray matter volume (GMV) in the left medial prefrontal cortex, in which the relationship was determined between inquiring about the life event questionnaire and changes in GMV for 2 years. That said, SLEs in adulthood are risk factors for diseases such as depression, and part of this risk is regulated by ways that change the physiology and structure of the brain. Davey et al. (2016) tried to clarify the relationship between stress and depression by studying twin experiments.
The etiology of depression is related to stress and HPA (Larrieu & Sandi, 2018). Trait anger affects depression by activating the HPA axis and sensitizing life stress events. Therefore, it is speculated that trait anger affects depression, as life stress events play a mediating role.
2.2 The influence of gender and age on the mediating model of trait anger affecting depression
2.2.1 The influence of gender on depression
Epidemiological studies have found that there are significant gender differences in the prevalence of MDD. The gender differences were mainly manifested in depression, with a lack of energy, psychomotor retardation and a pessimistic attitude toward the future (Sabic D., Sabic A.&Bacic B.A.,2021). Depressed women are approximately twice as likely as depressed men (Gin,S.,Malhi&J.,John,Mann,2018; Janet,S.H.&AmyH.M.,2020). The high risk of women suffering from MDD may be related to women's special physiological status, psychological status and sociopsychological factors (Huang Xiu, fang, et al., 2009). Female depression is related to their special physiology, such as menstruation, pregnancy, delivery and menopause, in which abnormal estrogen secretion is an important factor leading to menstrual syndrome, with prenatal restlessness, postpartum depression and menopausal depression (long Zhen, Zhao, 2014). Women's depression is also related to the emotional expression of their psychological factors. Dong Lina, Chen Hong & Wang Yu (2014) have shown that feminized individuals are more likely than masculine individuals to suppress their anger. They adopt contemplative coping styles and avoid conflict, resulting in lower life satisfaction, which leads to depression. Janet S. Hyde & Amy H., Mezulis (2020) analyzed vulnerability and susceptibility to depression in women based on the A (emotion), B (biology), and C (cognitive) models. It also explains the reasons for the gender differences in depression. The study analyzed biological vulnerability (genetic, puberty, physiological hormone fluctuations, etc. ), emotional vulnerability (temperament) and cognitive vulnerability (negative cognitive style, objective physical consciousness and meditation, etc.). Gender differences were in negative life events and sociocultural factors. Furthermore, the vulnerability-stress model is taken as the core theory, which provides a theoretical basis for the differential effects of depression in women under stress exposure. It can be seen that the influence of gender on the susceptibility to depression is affected by the subjects' physical, psychological and environmental factors, as well as by the micro and macro levels of society and culture (Gin S., Malhi & J. John Mann, 2018).
Due to the complexity of the influencing factors of gender differences in depression, it is speculated that the influence of gender on depression is dynamic and unstable. Some studies also believe that the gender difference in depression caused by gender bias is related to social culture because men are less likely to report that some symptoms of depression are nonmasculine (Sigmon S. T& Pells JJ., 2005). Motro D. &Ellis APJ. (2017) confirmed that in community samples that met the diagnostic criteria for MDD, 4 of the 26 symptoms were allowed or encouraged to be reported by female roles. Gender differences in depression are affected by social development and regional cultural differences. Jonathan M. Platt et al. (2020) showed that the gender depression gap narrowed in the cohort of subjects born between 1955 and 1994, which was influenced by the trend of economic and social status equality between men and women in the same period. Some studies also believe that there is no statistically significant difference in the prevalence of depression between genders (E. Stordal et al., 2001). E. Stordal et al. (2001) clarified that the difference may be due to differences in diagnostic methods, which was further explained by reported prevalence deviations due to different definitions of the concept of depression. Women tend to complain about their depression, physical discomfort and other related depressive symptoms, which are easy to find and diagnose in the early stage of depression or mild to moderate dysfunction (Huang Xiufang et al., 2009). It is speculated that based on the measurement results of the depression questionnaire, there are some gender differences in the scores of the depression scale between healthy people and patients with depression.
2.2.2 A moderating mediator with age as a moderating variable.
Gin S., M. &J John Mann (2018) found that the first episode of depression occurs from mid-adolescence to 40 s, but almost 40% of people experience the first episode of depression before the age of 20, with an average age of approximately 25 years old. MDD is a recurrent lifelong disease. Almost 80% of patients experience at least one attack in their lifetime. The probability of recurrence increases with the age of onset.
E. Stordal et al. (2001) found that the relationship between age and depression was very different and that the average level and number of cases of depression increased almost linearly with age. Alan Tuohy, Christina Knussen & Michael J. Wrennall (2005) believe that depression shows a U-shaped function with increasing age, and there is an upward trend in patients with depression after middle age. Studies have found that older people tend to be associated with common risk factors for depression, such as somatic symptoms, bereavement, loneliness, singleness and other diseases (E. Stordal et al., 2001). With increasing age, degenerative diseases and a decline in overall vitality play an important role in the somatization symptoms of depression (Guo Tong et al., 2022). Eleven percent of older people in New York City suffer from mental, cognitive or emotional disorders that lead to learning, memory and concentration difficulties (American Community Survey, 2016). The incidence of insomnia also increases significantly with age and is usually chronic compared with adults. Insomnia and depression have a strong two-way relationship: insomnia tends to accelerate the onset of depression, and if not treated properly, insomnia will also increase the chance of depression recurrence (Paul Sadlera, Suzanne McLarena, Britt Kleina &Megan Jenkinsa,2018). A study found that the older the age, the higher the prevalence of central nervous system diseases such as Parkinson's disease. (E. Jääskeläinen, et al., 2017) However, Parkinson's disease is considered a sign of bipolar disorder in the future. Therefore, with the increase in age, the aging of the body and the increase or decrease in the risk of progressive diseases, elderly individuals are more likely to suffer from depression. Stress events are the main stressors leading to depressive disorders, such as unemployment, emotional changes, divorce, bereavement, other family members suffering from serious illness or death serious illness, among which the incidence of depressive disorder is the highest in divorced and widowed people, with concentrated in the 30-50 age group (long Zhen, Zhao, 2014). Therefore, with increasing age, the probability of subjects experiencing the above stress events will be greatly increased. It is speculated that age, as a moderating variable, moderates the mediating effect of trait anger on depression. The specific manifestation is that age can moderate the psychological stress caused by life events by interacting with trait anger and then have an indirect effect on depression. As a result, it can be concluded that age is used as a moderating variable to moderate the front part of the mediating effect of trait anger on depression mediated by life events.
2.3 The present study
According to the literature, with the relationship among trait anger, depression, life events, age and gender variables, the following questions are proposed: as endogenous factors, how do trait anger and life events affect depression? and what's its mechanism? Is this mechanism universal for people with depression or for people including healthy people? How to make use of the influence mechanism of trait anger and life events on depression to develop a targeted intervention and regulation program will provide a basis for the prevention and treatment of depression. In view of the above problems, this paper proposes the following four hypotheses: hypothesis 1: In the control group, trait anger mediates depression with life events as mediating variables. Hypothesis 2: In the control group with depressive patients as subjects and the reference group with healthy people as subjects, there should be differences in the comparison of the mediating effect models between the two groups. Hypothesis 3: Age as a moderating variable interacts with trait anger in the control group, moderates the mediating effect on depression as a mediator of life events, and establishes a moderated mediating model. Hypothesis 4: The significant effect of gender on depression is different between the control group and the reference group.