According to the World Health Organisation (WHO, 2020), depression is a highly prevalent disorder with more than 300 million people affected globally. Unlike mood alterations that everyone can experience from time to time, depression may develop into the debilitating, potentially fatal illness. Causes of depression are complex, not entirely identified, and influenced by multiple sources including highly heterogeneous genetic and biological factors as well as psychosocial and environmental influences. Several models have been proposed to explicate origins of depression, based on biological, psychological, and environmental influences.
One of the well-established biological theories which sheds light on the aetiology of depression is the cytokine theory. Cytokines, which act primarily as cell signalling substances regulating inflammation in the immune system, may incite and aggravate depression. This statement was robustly supported by evidence of depression-like conditions that were induced by proinflammatory cytokines. Among other famous theories elucidating the causes of depression are the corticosteroid receptor (CRH) hypothesis of dysregulated hypothalamus–pituitary–adrenal (HPA) axis, resulting from stress and raised levels of stress hormones, and the monoaminergic theory of depression.
A large body of evidence from family and twin studies points to genetic contributions into causes of depression. A meta-analysis of Sullivan, Neale and Kendler (2000) reports the estimated heritability of depression at about 37% and reveals that the risk of depression in children of individuals suffering from depression is elevated threefold.
Numerous candidate genes have been explored to establish possible genetic links to depression; however, no solid genetic associations are defined, implying that depression is a complex heterogeneous illness. It seems highly plausible that the synchronised action of various genes and their interaction with each other and with environment governs the onset and development of depression.
Converging evidence suggests that environmental exposures such as exposure to air contamination may contribute to the onset of depression. Air contaminants can affect the activity of serotonergic and dopaminergic neurons and inflammatory cytokines, alter the morphology of the hippocampal neurons and cause oxidative stress in the striatum and prefrontal cortex.
A female preponderance in depression has been recently confirmed by Wang et al. (2016), highlighting that socioeconomic status and the severity of depression are negatively related. Among psychosocial factors, stressful severe life events, especially in early life, undoubtedly contribute to the onset of depression as confirmed in many studies. A fourfold increased risk of depression was associated with women who had been sexually or physically abused in childhood compared to those without such an experience.
Attachment theory of Bowlby (1977) may be a valuable basis to explore causes of depression – it claims that disrupted affectional bonds between children and caregivers are the key contributors to the development of psychopathology, including depression and anxiety.
However, despite the higher risk of depression in individuals with stressful childhood experiences, responses of people to the same type of adversity are different and this may be indicative of the co-influence of genetic factors. Caspi (2003) was among pioneers to establish an interaction between genes and environment, GxE interaction. He identified an important relationship between the serotonin gene (5-HTTLPR), stress, and depression. Individuals with the short allele of the 5-HTTLPR gene are remarkably susceptible to the adverse effects of childhood stress such as neglect or abuse.
Other possible pathways
Beck (2008) proposed the pathway to depression starts with genetic susceptibility. He posited that hyperreactivity of amygdala caused by the 5-HTTLPR polymorphism triggers negative bias and cognitive reactivity. Subsequently, this leads to the formation of dysfunctional beliefs and negative interpretations of experiences, which affect the HPA- axis and ultimately cause depression.
One more possible cause of depression can be explained by the developmental pathway from early conduct problems to adult depression.
Antidepressant medications have been known to alleviate symptoms of depression, especially in severe cases. Psychotherapeutic interventions have also been shown effective, either alone or combined with pharmacology. The major challenge, however, is 30% of treatment-resistant individuals.
Depression is a common illness that restricts psychosocial functioning and markedly decreases quality of life. It is a complex disorder resulting from the interaction of genes and environment. Uncertain origins and an unpredictable trajectory of depression often pose challenges for health care professionals. Further research into the female preponderance may shed more light on genesis of depression. Better insight into the aetiology of depression may be especially beneficial for the development of treatment for the treatment-resistant population.
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An instinctive drive for attachment is our fundamental survival mechanism in early childhood. According to Bowlby’s attachment theory (1969), an insecure, or unreliable and inconsistent attachment relationship with a caregiver in infancy decreases resilience in managing traumatic and stressful situations and makes children liable to mental breakdowns in critical circumstances, whereas a secure, or consistent and sensitive attachment style is a basis for a more constructive and optimistic trajectory of a child’s development. Insecure attachment, influenced by environmental and genetic factors, can be considered as a predisposition, or susceptibility to mental illness; however, the formation or reinstatement of a feeling of a secure attachment may improve resilience and enhance psychological wellbeing.
In general terms, the attachment can be defined as a specific mode of relating to other people, and attachment dynamics can be distinguished into secure and insecure. Insecure attachment patterns in childhood have been found to confer risks to the development of psychopathology in adulthood. Insecure attachment style is represented by insecure-avoidant, insecure-resistant and disorganised attachment types. Attachment behaviour is any type of action intended for getting a response from a preferred person, someone who is typically wiser or stronger. Bowlby (1977) observes that many psychiatric patients are insecure and immature people, who in stressful situations develop mental disorders. Research confirms that most of these individuals have experienced neglectful parenting, which is at the core of insecure attachment in infancy.
Strange situation, developed by Ainsworth in 1978, is a method which evaluates the attachment quality in children. Bowlby claimed that depending on caregivers’ attachment style, children form the internal working models which are conceived as the background for directing one’s views, emotions, and actions in the context of later-life interactions.
A substantial body of research, including longitudinal studies of the long-term consequences of insecure attachment relationships in early years on mental illness in later life, supported Bowlby’s ideas. Findings of Harris, Brown, and Bifulco (2012) demonstrate that the loss of a parent or long separation from parents in early life confers risk to adult depression. Coffino (2009) pointed out that the strongest predictor of depression in adulthood was the history of parental death between 5 and 10 years old.
Carlson, Egeland, and Sroufe (2009) investigated in a longitudinal study the developmental pathway of borderline personality disorder (BPD), from childhood to adulthood. They confirmed that repetitive contradictory cues representative of disorganised attachment in childhood, are strongly linked to a failure in regulatory tactics to manage stressful situations. The study reports that disorganised attachment, characterised by severe conditions of maltreatment in childhood, is linked to dissociative processes in later life, a marker in the development of BPD.
However, insecure attachment relationships do not result in psychopathology linearly, but other factors such as social and family life, intelligence, substance abuse are likely to augment the effects of insecure attachment on the way to a mental disorder.
While insecure attachment styles are conceived as risk factors for mental illness, the formation and regeneration of a feeling of security may improve mental health and resilience to stress. Mikulincer and Shaver (2012) report that the effects of an improved sense of security on different psychological indicators have been observed in the “security priming” trials that employed triggering mental associations with caring attachment figures. The researchers stated that security providers’ name priming alleviated symptoms of eating disorders, including distortion of body perception, in women diagnosed with eating disorders. There is also evidence of an improved patient’s psychological condition resulted from the feeling of security that was generated in a psychotherapeutic relationship.
Attachment in the context of psychology generally refers to the permanent emotional proximity between children and parents, or caregivers, which is necessary to prepare children for challenges of adulthood. Secure attachment in childhood facilitates the development of mental wellbeing and generates emotional resources for the management of difficulties, whereas insecure attachment style usually results in psychopathology. Formation or reinstatement of a feeling of secure attachment has been shown to enhance resilience to hardships and alleviate symptoms of mental illness.
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Emotion regulation processes manage manifestation, expression, strength, and duration of emotions, which critically influence our daily life and mental health. Adaptive strategies of emotion regulation tend to produce constructive outcomes such as reduced negative reactions and stress, while maladaptive strategies can substantially contribute to psychological disorders.
Attention control, acceptance, reappraisal, problem solving as well as rumination, avoidance, and suppression are among key strategies of emotion regulation. Research points out that maladaptive emotion control strategies, such as rumination, avoidance, and suppression are linked to psychopathology to a great extent as opposed to the adaptive emotion regulation methods – attention control, reappraisal, acceptance, and problem solving.
Attention control plays a significant role in decreasing adverse emotional effects of stressful events on people’s life. The strategy consists of two major components – the ability to focus on the task and the ability to shift attention, or multitask.
Problem solving refers to a deliberate attempt, a specific action such as brainstorming, which aims at modifying a stressful incident, adjusting to stressors or eliminating them. Studies demonstrate that a lack of problem-solving abilities may lead to anxiety, depression, eating disorders, and substance abuse. Problem-solving skill training is a component of cognitive-behavioural therapies (CBT) designed to treat these disorders.
Reappraisal involves benign and encouraging interpretations or appraisals of negative situations to transform their meaning and reduce their negative impact on emotions. Several models (e.g. Beck’s, 1976) showed that maladaptive appraisals are at the core of anxiety and depression; thus, CBT for anxiety and depression emphasise reappraisal skill learning.
The concept of mindfulness has been gaining an increasing interest. Although the mechanisms of mindfulness are yet to be understood and defined, researchers agree on its non-judgmental nature. Acceptance strategy is aimed at realising emotions without judging or altering them.
Imagery re-scripting has been suggested as one more adaptive strategy to regulate elicited emotions. Re-scripting aims at updating and correcting recollections of negative or traumatic experiences, as memories do not represent events in a static way. Beck, one of the fathers of cognitive therapy, adopted this method from P. Janet, who first presented it in 1919.
All these adaptive strategies have a similar effect of reducing daily distress by altering aversive components of emotions.
By contrast, suppression (suppressing negative thoughts and/or feelings) and avoidance (avoiding circumstances that may be unpleasant) are known as maladaptive strategies, which may result in anxiety, depression or substance abuse. Although suppression in the short-term perspective may decrease the external expression of emotion and, perhaps, the subjective experience of emotion, in the long run it will be ineffective for reducing emotional and physiological distress. As an alternative to suppression and avoidance, some people engage in rumination, or perseverative and repetitive negative thinking about their concerns; however, rumination has an inverse relationship with problem solving, and it is a key feature of a clinical problem.
To sum up, adaptive strategies such as attention control, acceptance, reappraisal, problem solving and re-scripting are linked to wellbeing, whereas maladaptive rumination, avoidance, and suppression are inefficient ways of coping with stress and are strongly associated with psychopathology.
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