In the fifth edition of the Diagnostic and Statistical Manual of Mental Disorders (DSM-5), Persistent Depressive Disorder (PDD) includes a spectrum of depressive mood disorders, dysthymia, and Major Depression Disorder (MDD) (1). PDD is a more common chronic mood disorder and is often more debilitating than episodic major depression. In DSM-5, this term includes several chronic depression states, including dysthymia with or without MMD episodes, chronic major depression, and recurrent major depression without improvement between episodes (2). Its most prominent feature is a depressive mood most of the day and on most days for at least two years (or at least one year for children and adolescents) (3). PDD includes at least two of the following six symptoms: Poor appetite or overeating, insomnia, lack of energy or fatigue, low self-esteem, poor concentration or difficulty in making decisions, and hopelessness. The patients are never free from these symptoms for two months (2). The difference between PDD and MDD is the complaint of being consistently depressed.
Most patients have an early onset, even from childhood or adolescence, and their disorder has already started when they reach the age of 20 to 30 years (4). Approximately, 20–30% of depressive disorders have a chronic course (5). Various epidemiological studies have demonstrated that the lifetime prevalence of depressive mood and several forms of chronic major depressive disorder is 0. 6 − 1% (6).
Depressive mood disorder is common in the general population and affects approximately 5–6% of individuals (4). However, the prevalence of chronic depression is higher in clinics; in some studies, it has been estimated at up to 33–50% (7, 8). In a meta-analysis, the overall prevalence of severe depression in Iranian adults was 8.2% (9, 10). Nonetheless, another study reported the prevalence of depression as 2.3% (11).
Some studies have demonstrated significant differences between dysthymia, major depression, and chronic major depression regarding comorbidity, personality, depression-related cognitions, coping styles, childhood problems, family psychopathology, and response to medication and psychotherapy (12). Due to the differences between chronic and non-chronic depression in different etiological factors on multiple variables related to their cause, this distinction is blurry at times. Although the information on the cause of PDD, including depression, is limited, there is consensus on the multifactorial nature of its cause (2). Various theories have explained depression and defined its biological, neurobiological, social, and psychological elements.
Among the psychological theories and contemporary models of depression, there is consensus that traumas early in life make the child susceptible to self and pathological object representations. In cases of physical and sexual abuse, the child internalizes a bad object, i.e., deserving to be abused, and anticipates abuse instead of being a victim. The damage to the child's personality in traumatic relationships with parents and other caregivers can lead to communication problems in adulthood (13).
Therefore, severe childhood traumas and cognitive, emotional, and interpersonal functions play a significant role in defining PDD. Childhood abuse includes all types of emotional or physical abuse, sexual abuse, neglect or negligence, commercial abuse, or any behavior leading to potential or actual harm to their health, survival, growth, or dignity (14). Childhood trauma includes any psychological event that suddenly breaks the capacity to "provide a sense of security and psychological integrity, and as a result, leads to excessive anxiety or helplessness, or its threat, which can damage psychological integrity" (15). Several studies have confirmed the relationship between childhood abuse and depressive symptoms in adulthood (16, 17). For example, a meta-analysis demonstrated that child neglect, emotional abuse, and physical abuse were associated with a higher incidence of depressive disorder in adulthood (18). Similar findings have contended that following physical abuse, physical neglect, and sexual abuse increases (16), the risk of depression in adulthood increases. Therefore, childhood trauma can be a significant risk factor for different depressive aspects, but its relationship with persistent depression is indisputably understudied.
On the other hand, there are few studies investigating the etiology of this disorder, and what remains explicitly in the dark is how these childhood traumas lead to depression in adulthood (19). In other words, there exists little evidence about mediating psychological processes in this regard.
One such influential component is social cognition problems. Defect in social cognition, referred to as preoperational thinking, plays a fundamental role in the pathogenesis of PDD (20). The term "preoperational thinking" was coined based on Piaget's children's cognitive development theory (21). McCullough believes that children with PDD who are in the preoperational stage of development have many similarities in emotional-cognitive processing, including 1) they imagine that they will always feel the way they do now (as opposed to one emotional reaction among many other emotional reactions), 2) they assume that all people will respond to them in the same way (as opposed to classifying an individual as one of the other types), and 3) they experience the present as a reproduction of the past (as opposed to seeing the present as an event amid a changing stream of events) (22). Through analyzing chronically depressed patients, McCullough observed that such patients were instead fixated on the preoperational stage. They tended to conclude directly from a preconceived notion without examining the thinking itself or analyzing other hypotheses. Moreover, they did not accept any logical explanation and behaved utterly self-centered. As a result, their inclusive self-centered views were presented as a monologue.
When these patients face adulthood duties, this fixation in the preoperational stage presents a problem, and chronically depressed patients do not realize the consequences of their interpersonal behavior (22). Some studies have demonstrated that chronically depressed patients remain in the preoperative stage due to childhood traumas or other unfavorable conditions; this is particularly prominent in patients with premature depression (23). When chronic depression develops, it can be assumed that emotional stress leads to a deterioration of cognitive-emotional performance and a return to the preoperational stage (22).
While cognitive deficits indicate difficulty in inferring the mental states of others, "preoperational thinking" and "perceptual disconnection" specifically describe the inability of chronically depressed patients to understand the consequences of their interpersonal behaviors for others. For example, if patients with PDD exhibit aggressive behavior and others respond with hostility, they view this hostile response, not as a predictable outcome of their aggressive behavior. As they have been hurt many times, they perceive it as proof that they are always hurt (24). Therefore, it can be deduced that social cognition problems characterized by preoperational thinking and interpersonal problems can be related to childhood traumas, on the one hand, and predict different types of depression, on the other hand. Nonetheless, their mediating roles have not been investigated independently. Therefore, these factors are investigated as mediating components in the current study.
On the other hand, there is evidence that attributional style is a stable cognitive risk factor related to acute stressors, which is significantly associated with depressive reactions following stressful life events. Early interpersonal trauma can be an extraordinarily adverse and uncontrollable life event. Therefore, it can be considered a primary model that leads to dysfunctional cognitive schemas such as helplessness and worthlessness (25, 26). Specifically, exposure to repeated or chronic maltreatment may lead to a tendency to attribute adverse events to internal, stable, and global causes (27). This depressive attributional style forms the central core of the theory of hopeless depression, which increases the risk of depression, according to Abrmentamson et al. (27, 28).
On the other hand, it is demonstrated that the chronic process of depression is associated with a higher level of hopelessness and external control power (29). The first evidence for the mediating role of depressive attributional style in the relationship between childhood maltreatment and depression was published by Scherholz et al. They also demonstrated that there are significant indirect effects of childhood maltreatment through the depressive attributional style on the number of depressive episodes and their severity (30). However, it is unclear whether it can also play a role in persistent depression. It can be asserted that mediator components are not merely limited to cognitive and interpersonal components, but emotional elements such as emotional regulation also play an essential role.
Emotion regulation is defined as "processes through which people manage their emotions consciously or unconsciously to respond to environmental demands appropriately" (31). Organizing emotional regulation has a reciprocal effect on the following abilities: 1) conscious understanding of emotions, 2) using emotions to recognize excitations, 3) correct labeling of emotions, 4) understanding emotions, 5) coping with negative emotions, 6) self-support when self-regulating one's own emotions, 7) changing negative emotions, and 8) facing emotional challenges to reach goals. Emotional regulation usually develops during childhood in interactions with principal caregivers. This development can be hindered in an abusive and neglectful environment, especially when the primary caregiver is abusive. Difficulties in emotion regulation, in turn, are associated with various types of psychopathologies, including depression (31, 32). Moreover, it is demonstrated that patients with depression struggle to regulate excitement. When they confront problems and experience negative emotions, they blame themselves, ruminate, consider the problems tragic, and suffer from depressive symptoms for a long time (33). Moreover, excessive rumination is an ineffective emotional regulation strategy that leads to long-term depression (34).
As discussed, interpersonal conflicts and characteristics are influential in the development and persistence of depression. Patients with depression repeatedly report stressful interpersonal interactions, often caused by their behavior. It has also been observed that in social interactions, patients with depressive disorders, particularly PDD, are more hostile and submissive than patients with episodic depression. This can negatively impact their performance and hinder therapeutic interventions (24). Although research in this field is scarce, it has been demonstrated that interpersonal challenges are the main link between childhood abuse and depression (35). Frequent interpersonal failure exposes a person to depression (36). For example, social isolation, avoidance, and submission are linked with depression (37). In sum, several points are noteworthy in this regard. First, although the literature on the relationship between childhood trauma and vulnerability to depression in adulthood is extensive, the ones that specifically explain the causes of persistent depression are minimal. Therefore, in this research, we aimed to investigate this relationship through a structural equation approach. Second, the literature demonstrates that childhood trauma does not always have direct effects. Therefore, considering that these effects are ongoing, the current study is valuable as it investigates how childhood trauma may lead to persistent depression and what mediators may be involved. Social cognition problems (preoperational thinking), interpersonal communication, emotion regulation, and documentation error may play prominent roles in this regard. Still, no research has been conducted in this field of study.
The Present Study
To shed light on persistent depressive disorder and the typology of influencing factors, the present study aimed to investigate the effect of childhood traumas on cognitive, emotional, and interpersonal functions and the severity of depressive symptoms. Then, the study investigated whether cognitive, emotional, and interpersonal functions can mediate the relationship between childhood traumas and the severity of persistent depressive disorder symptoms. In other words, the present study aimed to examine the fit of the structural model of persistent depressive disorder symptom severity based on childhood trauma and the mediating role of cognitive, emotional, and interpersonal functions.